diff --git a/composer.json b/composer.json
index 98f51871..f3b6066d 100644
--- a/composer.json
+++ b/composer.json
@@ -27,7 +27,8 @@
         "ibexa/core": "~4.3.0@dev",
         "ibexa/content-forms": "~4.3.0@dev",
         "ibexa/rest": "~4.3.0@dev",
-        "ibexa/http-cache": "~4.3.0@dev"
+        "ibexa/http-cache": "~4.3.0@dev",
+        "symfony/process": "^5.0"
     },
     "require-dev": {
         "ibexa/ci-scripts": "^0.2@dev",
@@ -56,6 +57,11 @@
             "Ibexa\\Tests\\Integration\\FieldTypeRichText\\": "tests/integration/"
         }
     },
+    "config": {
+        "allow-plugins": {
+            "*": false
+        }
+    },
     "scripts": {
         "fix-cs": "php-cs-fixer fix --config=.php-cs-fixer.php -v --show-progress=dots",
         "check-cs": "@fix-cs --dry-run",
diff --git a/src/bundle/Command/AbstractMultiProcessComand.php b/src/bundle/Command/AbstractMultiProcessComand.php
new file mode 100644
index 00000000..aa62fb94
--- /dev/null
+++ b/src/bundle/Command/AbstractMultiProcessComand.php
@@ -0,0 +1,366 @@
+<?php
+
+/**
+ * @copyright Copyright (C) Ibexa AS. All rights reserved.
+ * @license For full copyright and license information view LICENSE file distributed with this source code.
+ */
+declare(strict_types=1);
+
+namespace Ibexa\Bundle\FieldTypeRichText\Command;
+
+use Ibexa\Contracts\Core\Repository\PermissionResolver;
+use Ibexa\Contracts\Core\Repository\UserService;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Exception\RuntimeException;
+use Symfony\Component\Console\Helper\ProgressBar;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Input\InputOption;
+use Symfony\Component\Console\Output\OutputInterface;
+use Symfony\Component\Process\PhpExecutableFinder;
+use Symfony\Component\Process\Process;
+
+abstract class AbstractMultiProcessComand extends Command
+{
+    protected PermissionResolver $permissionResolver;
+
+    protected UserService $userService;
+
+    protected bool $hasProgressBar;
+
+    protected ProgressBar $progressBar;
+
+    /**
+     * @var \Symfony\Component\Console\Output\OutputInterface
+     */
+    protected OutputInterface $output;
+
+    /**
+     * @var bool
+     */
+    private bool $dryRun;
+
+    /**
+     * @var int
+     */
+    private int $maxProcesses;
+
+    /**
+     * @var \Symfony\Component\Process\Process[]
+     */
+    private $processes;
+
+    /**
+     * @var string
+     */
+    private mixed $user;
+
+    /**
+     * @var int
+     */
+    private int $iterationCount;
+
+    /**
+     * @var string
+     */
+    private string $environment;
+
+    public function __construct(
+        string $name = null,
+        PermissionResolver $permissionResolver,
+        UserService $userService
+    ) {
+        $this->permissionResolver = $permissionResolver;
+        $this->userService = $userService;
+        $this->dryRun = false;
+        $this->processes = [];
+
+        parent::__construct($name);
+    }
+
+    public function configure(): void
+    {
+        $this
+            ->addOption(
+                'user',
+                'u',
+                InputOption::VALUE_REQUIRED,
+                'Ibexa DXP username',
+                'admin'
+            )
+            ->addOption(
+                'dry-run',
+                null,
+                InputOption::VALUE_NONE,
+                'Run the converter without writing anything to the database'
+            )
+            ->addOption(
+                'no-progress',
+                null,
+                InputOption::VALUE_NONE,
+                'Disable the progress bar.'
+            )->addOption(
+                'processes',
+                null,
+                InputOption::VALUE_OPTIONAL,
+                'Number of child processes to run in parallel for iterations, if set to "auto" it will set to number of CPU cores -1, set to "1" or "0" to disable [default: "auto"]',
+                1
+            )->addOption(
+                'iteration-count',
+                null,
+                InputOption::VALUE_OPTIONAL,
+                'Number of objects to process in a single iteration. Set to avoid using too much memory [default: 10000]',
+                10000
+            );
+    }
+
+    protected function execute(InputInterface $input, OutputInterface $output): int
+    {
+        $this->user = (string) $input->getOption('user');
+        $this->permissionResolver->setCurrentUserReference(
+            $this->userService->loadUserByLogin($this->user)
+        );
+
+        $this->environment = (string) $input->getOption('env');
+
+        if ($input->getOption('dry-run')) {
+            $this->dryRun = true;
+        }
+        if ($this->isDryRun() && !$this->isChildProcess()) {
+            $output->writeln('Running in dry-run mode. No changes will actually be written to database');
+        }
+
+        $this->maxProcesses = (int) $input->getOption('processes');
+        if ($this->maxProcesses < 1) {
+            throw new RuntimeException('Invalid value for "--processes" given');
+        }
+
+        $this->iterationCount = (int) $input->getOption('iteration-count');
+        if ($this->iterationCount < 1) {
+            throw new RuntimeException('Invalid value for "--processes" given');
+        }
+
+        $this->hasProgressBar = !$this->isChildProcess() && !$input->getOption('no-progress');
+
+        $this->output = $output;
+
+        if ($this->isChildProcess()) {
+            $cursor = $this->constructCursorFromInputOptions();
+            $this->processData($cursor);
+        } else {
+            $this->output->writeln('Processing ' . $this->getObjectCount() . ' items.');
+            $this->output->writeln('Using ' . $this->getMaxProcesses() . ' concurrent processes and processing ' . $this->getIterationCount() . ' items per iteration');
+
+            $this->startProgressBar();
+
+            $this->iterate();
+            $this->waitForAllChildren();
+            $this->completed();
+        }
+
+        return self::SUCCESS;
+    }
+
+    /**
+     * This method should return the total number of items to process.
+     *
+     * @return int
+     */
+    abstract protected function getObjectCount(): int;
+
+    /**
+     * This method should process the subset of data, specified by the cursor.
+     *
+     * @param mixed $cursor
+     *
+     * @return mixed
+     */
+    abstract protected function processData(mixed $cursor);
+
+    /**
+     * This method is called once in every child process. It should return a cursor based on the input parameters
+     * to the subprocess command.
+     *
+     * @return mixed
+     */
+    abstract protected function constructCursorFromInputOptions(): mixed;
+
+    /**
+     * This method should return the command arguments that should be added when launching a new child process. It will
+     * typically be the arguments needed in order to construct the Cursor for the child process.
+     *
+     * @param mixed $cursor
+     *
+     * @return array
+     */
+    abstract protected function addChildProcessArguments(mixed $cursor): array;
+
+    /**
+     * The method should return true if the current process is a child process. This is typically detected using the
+     * custom command arguments used when launching a child proccess.
+     *
+     * @return bool
+     */
+    abstract protected function isChildProcess(): bool;
+
+    /**
+     * This is the method that is responsible for iterating over the dataset that is being processed and split it into
+     * chunks that can be processed by a child processes. In order to do that it will maintain a cursor and call
+     * createChildProcess() for each chunk.
+     */
+    abstract protected function iterate(): void;
+
+    /**
+     * This method is called when all data has been completed successfully.
+     */
+    abstract protected function completed(): void;
+
+    /**
+     * Anything written to standard output from the subprocess might be processed here
+     * Typically, you may print that on the console.
+     *
+     * @param string $output
+     */
+    abstract protected function processIncrementalOutput(string $output): void;
+
+    /**
+     * Anything written to standard error from the subprocess might be processed here
+     * Typically, you may print that on the console.
+     *
+     * @param string $output
+     */
+    abstract protected function processIncrementalErrorOutput(string $output): void;
+
+    public function isDryRun(): bool
+    {
+        return $this->dryRun;
+    }
+
+    public function getMaxProcesses(): int
+    {
+        return $this->maxProcesses;
+    }
+
+    public function getIterationCount(): int
+    {
+        return $this->iterationCount;
+    }
+
+    protected function doFork(): bool
+    {
+        return $this->maxProcesses > 1;
+    }
+
+    protected function waitForAvailableProcessSlot()
+    {
+        if (!$this->processSlotAvailable()) {
+            $this->waitForChild();
+        }
+    }
+
+    protected function processSlotAvailable(): bool
+    {
+        return \count($this->processes) < $this->getMaxProcesses();
+    }
+
+    private function waitForChild(): void
+    {
+        $childEnded = false;
+        while (!$childEnded) {
+            foreach ($this->processes as $pid => $p) {
+                $process = $p['process'];
+                $itemCount = $p['itemCount'];
+
+                if (!$process->isRunning()) {
+                    $this->processIncrementalOutput($process->getIncrementalOutput());
+                    $this->processIncrementalErrorOutput($process->getIncrementalErrorOutput());
+                    $childEnded = true;
+                    $exitStatus = $process->getExitCode();
+                    if ($exitStatus !== 0) {
+                        throw new RuntimeException(sprintf('Child process ended with status code %d. Terminating', $exitStatus));
+                    }
+                    unset($this->processes[$pid]);
+                    $this->advanceProgressBar($itemCount);
+                    break;
+                }
+                $this->processIncrementalOutput($process->getIncrementalOutput());
+                $this->processIncrementalErrorOutput($process->getIncrementalErrorOutput());
+            }
+            if (!$childEnded) {
+                sleep(1);
+            }
+        }
+    }
+
+    protected function waitForAllChildren(): void
+    {
+        while (count($this->processes) > 0) {
+            $this->waitForChild();
+        }
+        $this->finishProgressBar();
+    }
+
+    protected function createChildProcess(mixed $cursor, int $itemCount)
+    {
+        if ($this->doFork()) {
+            $this->waitForAvailableProcessSlot();
+
+            $phpBinaryFinder = new PhpExecutableFinder();
+            $phpBinaryPath = $phpBinaryFinder->find();
+
+            $arguments = [
+                $phpBinaryPath,
+                'bin/console',
+                $this->getName(),
+                "--user=$this->user",
+            ];
+
+            $arguments[] = '--env=' . $this->environment;
+
+            if ($this->isDryRun()) {
+                $arguments[] = '--dry-run';
+            }
+            if ($this->output->isVerbose()) {
+                $arguments[] = '-v';
+            } elseif ($this->output->isVeryVerbose()) {
+                $arguments[] = '-vv';
+            } elseif ($this->output->isDebug()) {
+                $arguments[] = '-vvv';
+            }
+
+            $arguments = array_merge($arguments, $this->addChildProcessArguments($cursor));
+
+            $process = new Process($arguments);
+            $process->start();
+            $this->processes[$process->getPid()] = [
+                'process' => $process,
+                'itemCount' => $itemCount,
+            ];
+        } else {
+            $this->processData($cursor);
+            $this->advanceProgressBar($itemCount);
+        }
+    }
+
+    private function startProgressBar()
+    {
+        if ($this->hasProgressBar) {
+            $this->progressBar = new ProgressBar($this->output, $this->getObjectCount());
+            $this->progressBar->setFormat('very_verbose');
+            $this->progressBar->start();
+        }
+    }
+
+    protected function advanceProgressBar($step)
+    {
+        if ($this->hasProgressBar) {
+            $this->progressBar->advance($step);
+        }
+    }
+
+    protected function finishProgressBar()
+    {
+        if ($this->hasProgressBar) {
+            $this->progressBar->finish();
+        }
+    }
+}
diff --git a/src/bundle/Command/MigrateNamespacesCommand.php b/src/bundle/Command/MigrateNamespacesCommand.php
new file mode 100644
index 00000000..efb1a064
--- /dev/null
+++ b/src/bundle/Command/MigrateNamespacesCommand.php
@@ -0,0 +1,206 @@
+<?php
+
+/**
+ * @copyright Copyright (C) Ibexa AS. All rights reserved.
+ * @license For full copyright and license information view LICENSE file distributed with this source code.
+ */
+declare(strict_types=1);
+
+namespace Ibexa\Bundle\FieldTypeRichText\Command;
+
+use Ibexa\Contracts\Core\Repository\PermissionResolver;
+use Ibexa\Contracts\Core\Repository\UserService;
+use Ibexa\FieldTypeRichText\Persistence\Legacy\ContentModelGateway as Gateway;
+use Symfony\Component\Console\Exception\RuntimeException;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Input\InputOption;
+use Symfony\Component\Console\Output\OutputInterface;
+
+final class MigrateNamespacesCommand extends AbstractMultiProcessComand
+{
+    protected static $defaultName = 'ibexa:migrate:richtext-namespaces';
+
+    private Gateway $gateway;
+
+    private ?int $cursorStart;
+
+    private ?int $cursorStop;
+
+    private ?int $objectCount;
+
+    private int $convertDone;
+
+    private int $convertSkipped;
+
+    public function __construct(
+        PermissionResolver $permissionResolver,
+        UserService $userService,
+        Gateway $gateway
+    ) {
+        $this->objectCount = null;
+        $this->convertDone = 0;
+        $this->convertSkipped = 0;
+        parent::__construct(null, $permissionResolver, $userService);
+        $this->gateway = $gateway;
+    }
+
+    public function configure(): void
+    {
+        parent::configure();
+
+        $this
+            ->setName(self::$defaultName)
+            ->addOption(
+                'cursor-start',
+                null,
+                InputOption::VALUE_REQUIRED,
+                'Internal option - only used for subprocesses',
+            )
+            ->addOption(
+                'cursor-stop',
+                null,
+                InputOption::VALUE_REQUIRED,
+                'Internal option - only used for subprocesses',
+            );
+    }
+
+    protected function execute(InputInterface $input, OutputInterface $output): int
+    {
+        $this->cursorStart = $input->getOption('cursor-start') !== null ? (int) $input->getOption('cursor-start') : null;
+        $this->cursorStop = $input->getOption('cursor-stop') !== null ? (int) $input->getOption('cursor-stop') : null;
+
+        // Check that both --cursor-start and cursor-start are set, or neither
+        if (($this->cursorStart === null) xor ($this->cursorStop === null)) {
+            throw new RuntimeException('The options --cursor-start and -cursor-stop are only for internal use !');
+        }
+
+        parent::execute($input, $output);
+
+        return self::SUCCESS;
+    }
+
+    protected function getObjectCount(): int
+    {
+        if ($this->objectCount === null) {
+            $this->output->writeln('Fetching number of objects to process. This might take several minutes if you have many records in ezcontentobject_attribute table.');
+            $this->objectCount = $this->gateway->countRichtextAttributes();
+        }
+
+        return $this->objectCount;
+    }
+
+    protected function iterate(): void
+    {
+        $limit = $this->getIterationCount();
+        $cursor = [
+            'start' => -1,
+            'stop' => null,
+        ];
+
+        $contentAttributeIDs = $this->gateway->getContentObjectAttributeIds($cursor['start'], $limit);
+        $cursor['stop'] = $this->getNextCursor($contentAttributeIDs);
+        while ($cursor['stop'] !== null) {
+            $this->createChildProcess($cursor, count($contentAttributeIDs));
+
+            $cursor['start'] = $cursor['stop'];
+            $contentAttributeIDs = $this->gateway->getContentObjectAttributeIds($cursor['start'], $limit);
+            $cursor['stop'] = $this->getNextCursor($contentAttributeIDs);
+        }
+    }
+
+    protected function completed(): void
+    {
+        $this->output->writeln(PHP_EOL . 'Completed');
+        $this->output->writeln("Converted $this->convertDone field attributes(s)");
+        $this->output->writeln("Skipped $this->convertSkipped field attributes(s) which already had correct namespaces");
+    }
+
+    protected function getNextCursor(array $contentAttributeIDs): ?int
+    {
+        $lastId = count($contentAttributeIDs) > 0 ? end($contentAttributeIDs)['id'] : null;
+
+        return $lastId;
+    }
+
+    protected function processData($cursor)
+    {
+        $this->updateNamespacesInColumns($cursor['start'], $cursor['stop']);
+        if ($this->isChildProcess()) {
+            $this->output->writeln("Converted:$this->convertDone");
+            $this->output->writeln("Skipped:$this->convertSkipped");
+        }
+    }
+
+    protected function constructCursorFromInputOptions(): mixed
+    {
+        return [
+            'start' => $this->cursorStart,
+            'stop' => $this->cursorStop,
+        ];
+    }
+
+    protected function addChildProcessArguments($cursor): array
+    {
+        return [
+            '--cursor-start=' . $cursor['start'],
+            '--cursor-stop=' . $cursor['stop'],
+        ];
+    }
+
+    protected function isChildProcess(): bool
+    {
+        return $this->cursorStart !== null || $this->cursorStop !== null;
+    }
+
+    protected function processIncrementalOutput(string $output): void
+    {
+        if ($output !== '') {
+            $lines = explode(PHP_EOL, $output);
+            foreach ($lines as $line) {
+                if (strpos($line, 'Converted:') === 0) {
+                    $this->convertDone += (int) substr($line, strpos($line, ':') + 1);
+                } elseif (strpos($line, 'Skipped:') === 0) {
+                    $this->convertSkipped += (int) substr($line, strpos($line, ':') + 1);
+                } elseif ($line !== '') {
+                    $this->output->writeln($line);
+                }
+            }
+        }
+    }
+
+    protected function processIncrementalErrorOutput(string $output): void
+    {
+        $this->output->write($output);
+    }
+
+    public static function migrateNamespaces(string $xmlText)
+    {
+        $xmlText = str_replace('xmlns:ezxhtml="http://ez.no/xmlns/ezpublish/docbook/xhtml"', 'xmlns:ezxhtml="http://ibexa.co/xmlns/dxp/docbook/xhtml"', $xmlText);
+        $xmlText = str_replace('xmlns:ezcustom="http://ez.no/xmlns/ezpublish/docbook/custom"', 'xmlns:ezcustom="http://ibexa.co/xmlns/dxp/docbook/custom"', $xmlText);
+        $xmlText = str_replace('ezxhtml:class="ez-embed-type-image"', 'ezxhtml:class="ibexa-embed-type-image"', $xmlText);
+        $xmlText = str_replace('xmlns:ez="http://ez.no/xmlns/ezpublish/docbook"', 'xmlns:ez="http://ibexa.co/xmlns/ezpublish/docbook"', $xmlText);
+        $xmlText = str_replace('xmlns:a="http://ez.no/xmlns/annotation"', 'xmlns:a="http://ibexa.co/xmlns/annotation"', $xmlText);
+        $xmlText = str_replace('xmlns:m="http://ez.no/xmlns/module"', 'xmlns:m="http://ibexa.co/xmlns/module"', $xmlText);
+
+        return $xmlText;
+    }
+
+    protected function updateNamespacesInColumns(int $contentAttributeIdStart, int $contentAttributeIdStop): void
+    {
+        $contentAttributes = $this->gateway->getContentObjectAttributes($contentAttributeIdStart, $contentAttributeIdStop);
+
+        foreach ($contentAttributes as $contentAttribute) {
+            //$orgString = $contentAttribute['data_text'];
+            $newXml = self::migrateNamespaces($contentAttribute['data_text']);
+
+            if ($newXml !== $contentAttribute['data_text']) {
+                ++$this->convertDone;
+                if (!$this->isDryRun()) {
+                    $this->gateway->updateContentObjectAttribute($newXml, $contentAttribute['contentobject_id'], $contentAttribute['id'], $contentAttribute['version'], $contentAttribute['language_code']);
+                }
+            } else {
+                ++$this->convertSkipped;
+            }
+        }
+    }
+}
diff --git a/src/bundle/DependencyInjection/Compiler/RichTextHtml5ConverterPass.php b/src/bundle/DependencyInjection/Compiler/RichTextHtml5ConverterPass.php
index 756310b4..f62d74be 100644
--- a/src/bundle/DependencyInjection/Compiler/RichTextHtml5ConverterPass.php
+++ b/src/bundle/DependencyInjection/Compiler/RichTextHtml5ConverterPass.php
@@ -37,6 +37,14 @@ public function process(ContainerBuilder $container)
             );
             $this->setConverterDefinitions($taggedInputServiceIds, $html5InputConverterDefinition);
         }
+
+        if ($container->hasDefinition('ibexa.richtext.converter.edit.xhtml5')) {
+            $html5EditConverterDefinition = $container->getDefinition('ibexa.richtext.converter.edit.xhtml5');
+            $taggedInputServiceIds = $container->findTaggedServiceIds(
+                'ibexa.field_type.richtext.converter.edit.xhtml5'
+            );
+            $this->setConverterDefinitions($taggedInputServiceIds, $html5EditConverterDefinition);
+        }
     }
 
     /**
diff --git a/src/bundle/Resources/config/fieldtype_services.yaml b/src/bundle/Resources/config/fieldtype_services.yaml
index 39ec7f2f..20f8a76f 100644
--- a/src/bundle/Resources/config/fieldtype_services.yaml
+++ b/src/bundle/Resources/config/fieldtype_services.yaml
@@ -139,9 +139,31 @@ services:
         tags:
             - {name: ibexa.field_type.richtext.converter.input.xhtml5, priority: 10}
 
+    # Aggregate converter for XHTML5 edit that other converters register to
+    # through 'ibexa.field_type.richtext.converter.edit.xhtml5' service tag.
+    ibexa.richtext.converter.edit.xhtml5:
+        class: Ibexa\FieldTypeRichText\RichText\Converter\Aggregate
+        lazy: true
+
     Ibexa\FieldTypeRichText\RichText\Converter\Html5Edit:
         class: Ibexa\FieldTypeRichText\RichText\Converter\Html5Edit
         arguments:
             - '%ibexa.field_type.richtext.converter.edit.xhtml5.resources%'
             - '@ibexa.config.resolver'
+        tags:
+            - {name: ibexa.field_type.richtext.converter.edit.xhtml5, priority: 100}
 
+    # Note: should run before xsl transformation
+    Ibexa\FieldTypeRichText\RichText\Converter\EzNoNamespace:
+        class: Ibexa\FieldTypeRichText\RichText\Converter\EzNoNamespace
+        tags:
+            - {name: ibexa.field_type.richtext.converter.output.xhtml5, priority: -15}
+            - {name: ibexa.field_type.richtext.converter.edit.xhtml5, priority: -15}
+
+    Ibexa\Bundle\FieldTypeRichText\Command\MigrateNamespacesCommand:
+        autowire: true
+        autoconfigure: true
+
+    Ibexa\FieldTypeRichText\Persistence\Legacy\ContentModelGateway:
+        arguments:
+            $connection: '@ibexa.persistence.connection'
diff --git a/src/bundle/Resources/config/form.yaml b/src/bundle/Resources/config/form.yaml
index ba37f313..0857678c 100644
--- a/src/bundle/Resources/config/form.yaml
+++ b/src/bundle/Resources/config/form.yaml
@@ -6,12 +6,12 @@ services:
 
     Ibexa\FieldTypeRichText\Form\Type\RichTextFieldType:
         arguments:
-            $docbookToXhtml5EditConverter: '@Ibexa\FieldTypeRichText\RichText\Converter\Html5Edit'
+            $docbookToXhtml5EditConverter: '@ibexa.richtext.converter.edit.xhtml5'
             $fieldTypeService: '@ibexa.api.service.field_type'
 
     Ibexa\FieldTypeRichText\Form\Type\RichTextType:
         arguments:
-            $docbookToXhtml5EditConverter: '@Ibexa\FieldTypeRichText\RichText\Converter\Html5Edit'
+            $docbookToXhtml5EditConverter: '@ibexa.richtext.converter.edit.xhtml5'
 
     Ibexa\FieldTypeRichText\Validator\Constraints\RichTextValidator:
         tags:
diff --git a/src/bundle/Resources/config/rest.yaml b/src/bundle/Resources/config/rest.yaml
index 7aae8148..573bbad0 100644
--- a/src/bundle/Resources/config/rest.yaml
+++ b/src/bundle/Resources/config/rest.yaml
@@ -6,6 +6,6 @@ services:
 
     Ibexa\FieldTypeRichText\REST\FieldTypeProcessor\RichTextProcessor:
         arguments:
-            - '@Ibexa\FieldTypeRichText\RichText\Converter\Html5Edit'
+            - '@ibexa.richtext.converter.edit.xhtml5'
         tags:
             - { name: ibexa.rest.field_type.processor, alias: ezrichtext }
diff --git a/src/bundle/Resources/config/templating.yaml b/src/bundle/Resources/config/templating.yaml
index 42d26faf..67d1f93b 100644
--- a/src/bundle/Resources/config/templating.yaml
+++ b/src/bundle/Resources/config/templating.yaml
@@ -7,7 +7,7 @@ services:
     Ibexa\Bundle\FieldTypeRichText\Templating\Twig\Extension\RichTextConverterExtension:
         arguments:
             $richTextOutputConverter: '@ibexa.richtext.converter.output.xhtml5'
-            $richTextEditConverter: '@Ibexa\FieldTypeRichText\RichText\Converter\Html5Edit'
+            $richTextEditConverter: '@ibexa.richtext.converter.edit.xhtml5'
 
     Ibexa\Bundle\FieldTypeRichText\Templating\Twig\Extension\YoutubeIdExtractorExtension: ~
 
diff --git a/src/lib/Persistence/Legacy/ContentModelGateway.php b/src/lib/Persistence/Legacy/ContentModelGateway.php
new file mode 100644
index 00000000..aaab6739
--- /dev/null
+++ b/src/lib/Persistence/Legacy/ContentModelGateway.php
@@ -0,0 +1,147 @@
+<?php
+
+/**
+ * @copyright Copyright (C) Ibexa AS. All rights reserved.
+ * @license For full copyright and license information view LICENSE file distributed with this source code.
+ */
+declare(strict_types=1);
+
+namespace Ibexa\FieldTypeRichText\Persistence\Legacy;
+
+use Doctrine\DBAL\Connection;
+
+class ContentModelGateway
+{
+    public const DB_TABLE_CONTENTOBJECT_ATTRIBUTE = 'ezcontentobject_attribute';
+    public const FIELD_TYPE_IDENTIFIER = 'ezrichtext';
+
+    /**
+     * @var \Doctrine\DBAL\Connection
+     */
+    private $connection;
+
+    public function __construct(Connection $connection)
+    {
+        $this->connection = $connection;
+    }
+
+    public function countRichtextAttributes(): int
+    {
+        $query = $this->connection->createQueryBuilder();
+        $query->select('count(distinct a.id)')
+            ->from(self::DB_TABLE_CONTENTOBJECT_ATTRIBUTE, 'a')
+            ->where(
+                $query->expr()->eq(
+                    'a.data_type_string',
+                    ':data_type'
+                )
+            )
+            ->setParameter(':data_type', self::FIELD_TYPE_IDENTIFIER);
+
+        $statement = $query->execute();
+
+        return (int) $statement->fetchOne();
+    }
+
+    public function getContentObjectAttributeIds(int $startId, int $limit): array
+    {
+        $query = $this->connection->createQueryBuilder();
+        $query->select('a.id')
+            ->from(self::DB_TABLE_CONTENTOBJECT_ATTRIBUTE, 'a')
+            ->where(
+                $query->expr()->eq(
+                    'a.data_type_string',
+                    ':data_type'
+                )
+            )->andWhere(
+                $query->expr()->gt(
+                    'a.id',
+                    ':start_id'
+                )
+            )
+            ->groupBy('a.id')
+            ->orderBy('a.id')
+            ->setMaxResults($limit)
+            ->setParameter(':data_type', self::FIELD_TYPE_IDENTIFIER)
+            ->setParameter(':start_id', $startId);
+
+        $statement = $query->execute();
+
+        return $statement->fetchAllAssociative();
+    }
+
+    public function getContentObjectAttributes(int $contentAttributeIdStart, int $contentAttributeIdStop): array
+    {
+        $query = $this->connection->createQueryBuilder();
+        $query->select('a.id, a.version, a.contentobject_id, a.language_code, a.data_text')
+            ->from(self::DB_TABLE_CONTENTOBJECT_ATTRIBUTE, 'a')
+            ->where(
+                $query->expr()->eq(
+                    'a.data_type_string',
+                    ':data_type'
+                )
+            )->andWhere(
+                $query->expr()->gt(
+                    'a.id',
+                    ':content_attribute_id_start'
+                )
+            )->andWhere(
+                $query->expr()->lte(
+                    'a.id',
+                    ':content_attribute_id_stop'
+                )
+            )
+            ->orderBy('a.id')
+            ->setParameter(':data_type', self::FIELD_TYPE_IDENTIFIER)
+            ->setParameter(':content_attribute_id_start', $contentAttributeIdStart)
+            ->setParameter(':content_attribute_id_stop', $contentAttributeIdStop);
+
+        $statement = $query->execute();
+
+        return $statement->fetchAllAssociative();
+    }
+
+    public function updateContentObjectAttribute($xml, $contentId, $attributeId, $version, $languageCode)
+    {
+        $updateQuery = $this->connection->createQueryBuilder();
+        $updateQuery->update('ezcontentobject_attribute')
+            ->set('data_text', ':newxml')
+            ->where(
+                $updateQuery->expr()->eq(
+                    'data_type_string',
+                    ':datatypestring'
+                )
+            )
+            ->andWhere(
+                $updateQuery->expr()->eq(
+                    'contentobject_id',
+                    ':contentId'
+                )
+            )
+            ->andWhere(
+                $updateQuery->expr()->eq(
+                    'id',
+                    ':attributeid'
+                )
+            )
+            ->andWhere(
+                $updateQuery->expr()->eq(
+                    'version',
+                    ':version'
+                )
+            )
+            ->andWhere(
+                $updateQuery->expr()->eq(
+                    'language_code',
+                    ':languagecode'
+                )
+            )
+            ->setParameter(':newxml', $xml)
+            ->setParameter(':datatypestring', self::FIELD_TYPE_IDENTIFIER)
+            ->setParameter(':contentId', $contentId)
+            ->setParameter(':attributeid', $attributeId)
+            ->setParameter(':version', $version)
+            ->setParameter(':languagecode', $languageCode);
+        $updateQuery->execute();
+    }
+}
diff --git a/src/lib/RichText/Converter/EzNoNamespace.php b/src/lib/RichText/Converter/EzNoNamespace.php
new file mode 100644
index 00000000..0df928bc
--- /dev/null
+++ b/src/lib/RichText/Converter/EzNoNamespace.php
@@ -0,0 +1,25 @@
+<?php
+
+/**
+ * @copyright Copyright (C) Ibexa AS. All rights reserved.
+ * @license For full copyright and license information view LICENSE file distributed with this source code.
+ */
+declare(strict_types=1);
+
+namespace Ibexa\FieldTypeRichText\RichText\Converter;
+
+use DOMDocument;
+use Ibexa\Bundle\FieldTypeRichText\Command\MigrateNamespacesCommand;
+use Ibexa\Contracts\FieldTypeRichText\RichText\Converter;
+
+class EzNoNamespace implements Converter
+{
+    public function convert(DOMDocument $xmlDoc)
+    {
+        $xml = $xmlDoc->saveXML();
+        $xml = MigrateNamespacesCommand::migrateNamespaces($xml);
+        $xmlDoc->loadXML($xml);
+
+        return $xmlDoc;
+    }
+}
diff --git a/tests/bundle/Command/MigrateNamespacesCommandTest.php b/tests/bundle/Command/MigrateNamespacesCommandTest.php
new file mode 100644
index 00000000..f009219c
--- /dev/null
+++ b/tests/bundle/Command/MigrateNamespacesCommandTest.php
@@ -0,0 +1,124 @@
+<?php
+
+/**
+ * @copyright Copyright (C) Ibexa AS. All rights reserved.
+ * @license For full copyright and license information view LICENSE file distributed with this source code.
+ */
+declare(strict_types=1);
+
+namespace Ibexa\Tests\Bundle\FieldTypeRichText\Command;
+
+use Ibexa\Bundle\FieldTypeRichText\Command\MigrateNamespacesCommand;
+use PHPUnit\Framework\TestCase;
+
+class MigrateNamespacesCommandTest extends TestCase
+{
+    public function providerMigrateNamespaces()
+    {
+        return [
+            [
+                '<?xml version="1.0" encoding="UTF-8"?>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:ezcustom="http://ez.no/xmlns/ezpublish/docbook/custom" xmlns:ezxhtml="http://ez.no/xmlns/ezpublish/docbook/xhtml" xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0-variant ezpublish-1.0">
+    <para ezxhtml:class="custom_class">
+        This is some text in custom_class with
+        <emphasis>something in bold</emphasis>
+        and the end.
+    </para>
+</section>
+',
+                '<?xml version="1.0" encoding="UTF-8"?>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:ezcustom="http://ibexa.co/xmlns/dxp/docbook/custom" xmlns:ezxhtml="http://ibexa.co/xmlns/dxp/docbook/xhtml" xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0-variant ezpublish-1.0">
+    <para ezxhtml:class="custom_class">
+        This is some text in custom_class with
+        <emphasis>something in bold</emphasis>
+        and the end.
+    </para>
+</section>
+',
+            ],
+            [
+                '<?xml version="1.0" encoding="UTF-8"?>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:ezcustom="http://ez.no/xmlns/ezpublish/docbook/custom" xmlns:ezxhtml="http://ez.no/xmlns/ezpublish/docbook/xhtml" xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0-variant ezpublish-1.0">
+    <para ezxhtml:class="custom_class">
+        This is some text
+    </para>
+    <ezembed xlink:href="ezcontent://78" view="embed" ezxhtml:class="ez-embed-type-image">
+      <ezconfig>
+         <ezvalue key="size">medium</ezvalue>
+      </ezconfig>
+   </ezembed>
+</section>
+',
+                '<?xml version="1.0" encoding="UTF-8"?>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:ezcustom="http://ibexa.co/xmlns/dxp/docbook/custom" xmlns:ezxhtml="http://ibexa.co/xmlns/dxp/docbook/xhtml" xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0-variant ezpublish-1.0">
+    <para ezxhtml:class="custom_class">
+        This is some text
+    </para>
+    <ezembed xlink:href="ezcontent://78" view="embed" ezxhtml:class="ibexa-embed-type-image">
+      <ezconfig>
+         <ezvalue key="size">medium</ezvalue>
+      </ezconfig>
+   </ezembed>
+</section>
+',
+            ],
+            [
+                '<?xml version="1.0" encoding="UTF-8"?>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:ez="http://ez.no/xmlns/ezpublish/docbook" xmlns:ezcustom="http://ez.no/xmlns/ezpublish/docbook/custom" xmlns:ezxhtml="http://ez.no/xmlns/ezpublish/docbook/xhtml" xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0-variant ezpublish-1.0">
+    <para>
+        This is some text
+    </para>
+</section>
+',
+                '<?xml version="1.0" encoding="UTF-8"?>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:ez="http://ibexa.co/xmlns/ezpublish/docbook" xmlns:ezcustom="http://ibexa.co/xmlns/dxp/docbook/custom" xmlns:ezxhtml="http://ibexa.co/xmlns/dxp/docbook/xhtml" xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0-variant ezpublish-1.0">
+    <para>
+        This is some text
+    </para>
+</section>
+',
+            ],
+            [
+                '<?xml version="1.0" encoding="UTF-8"?>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:a="http://ez.no/xmlns/annotation" xmlns:ezcustom="http://ez.no/xmlns/ezpublish/docbook/custom" xmlns:ezxhtml="http://ez.no/xmlns/ezpublish/docbook/xhtml" xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0-variant ezpublish-1.0">
+    <para>
+        This is some text
+    </para>
+</section>
+',
+                '<?xml version="1.0" encoding="UTF-8"?>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:a="http://ibexa.co/xmlns/annotation" xmlns:ezcustom="http://ibexa.co/xmlns/dxp/docbook/custom" xmlns:ezxhtml="http://ibexa.co/xmlns/dxp/docbook/xhtml" xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0-variant ezpublish-1.0">
+    <para>
+        This is some text
+    </para>
+</section>
+',
+            ],
+            [
+                '<?xml version="1.0" encoding="UTF-8"?>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:m="http://ez.no/xmlns/module" xmlns:ezcustom="http://ez.no/xmlns/ezpublish/docbook/custom" xmlns:ezxhtml="http://ez.no/xmlns/ezpublish/docbook/xhtml" xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0-variant ezpublish-1.0">
+    <para>
+        This is some text
+    </para>
+</section>
+',
+                '<?xml version="1.0" encoding="UTF-8"?>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:m="http://ibexa.co/xmlns/module" xmlns:ezcustom="http://ibexa.co/xmlns/dxp/docbook/custom" xmlns:ezxhtml="http://ibexa.co/xmlns/dxp/docbook/xhtml" xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0-variant ezpublish-1.0">
+    <para>
+        This is some text
+    </para>
+</section>
+',
+            ],
+        ];
+    }
+
+    /**
+     * @dataProvider providerMigrateNamespaces
+     */
+    public function testMigrateNamespaces(string $xmlTextSource, string $xmlTestExpected): void
+    {
+        $migratedXml = MigrateNamespacesCommand::migrateNamespaces($xmlTextSource);
+        self::assertEquals($xmlTestExpected, $migratedXml, 'Docbook with ez.no namespaces was not converted correctly');
+    }
+}
diff --git a/tests/lib/RichText/Converter/AggregateTest.php b/tests/lib/RichText/Converter/AggregateTest.php
index 42e8a780..ee5683c4 100644
--- a/tests/lib/RichText/Converter/AggregateTest.php
+++ b/tests/lib/RichText/Converter/AggregateTest.php
@@ -14,8 +14,10 @@
 use Ibexa\Contracts\FieldTypeRichText\RichText\RendererInterface;
 use Ibexa\Core\MVC\Symfony\Routing\UrlAliasRouter;
 use Ibexa\FieldTypeRichText\RichText\Converter\Aggregate;
+use Ibexa\FieldTypeRichText\RichText\Converter\EzNoNamespace;
 use Ibexa\FieldTypeRichText\RichText\Converter\Link;
 use Ibexa\FieldTypeRichText\RichText\Converter\Render\Template;
+use Ibexa\FieldTypeRichText\RichText\Converter\Xslt;
 use PHPUnit\Framework\TestCase;
 
 class AggregateTest extends TestCase
@@ -97,6 +99,140 @@ public function providerConvertWithLinkInCustomTag(): array
             ],
         ];
     }
+
+    public function providerConvertDocbookToHtmlEditWithEznoNamespace(): array
+    {
+        return [
+            [
+                '<?xml version="1.0" encoding="UTF-8"?>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:ezcustom="http://ez.no/xmlns/ezpublish/docbook/custom" xmlns:ezxhtml="http://ez.no/xmlns/ezpublish/docbook/xhtml" xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0-variant ezpublish-1.0">
+    <para ezxhtml:class="custom_class">
+        This is some text in custom_class with
+        <emphasis>something in bold</emphasis>
+        and the end.
+    </para>
+</section>
+',
+                '<?xml version="1.0" encoding="UTF-8"?>
+<section xmlns="http://ibexa.co/namespaces/ezpublish5/xhtml5/edit">
+    <p class="custom_class">
+        This is some text in custom_class with
+        <em>something in bold</em>
+        and the end.
+    </p>
+</section>
+',
+            ],
+            [
+                '<?xml version="1.0" encoding="UTF-8"?>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:ezcustom="http://ez.no/xmlns/ezpublish/docbook/custom" xmlns:ezxhtml="http://ez.no/xmlns/ezpublish/docbook/xhtml" xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0-variant ezpublish-1.0">
+    <para ezxhtml:class="custom_class">
+        This is some text
+    </para>
+    <ezembed xlink:href="ezcontent://78" view="embed" ezxhtml:class="ez-embed-type-image">
+      <ezconfig>
+         <ezvalue key="size">medium</ezvalue>
+      </ezconfig>
+   </ezembed>
+</section>
+',
+                '<?xml version="1.0" encoding="UTF-8"?>
+<section xmlns="http://ibexa.co/namespaces/ezpublish5/xhtml5/edit">
+    <p class="custom_class">
+        This is some text
+    </p>
+    <div class="ibexa-embed-type-image" data-href="ezcontent://78" data-ezelement="ezembed" data-ezview="embed">
+      <span data-ezelement="ezconfig">
+         <span data-ezelement="ezvalue" data-ezvalue-key="size">medium</span>
+      </span>
+   </div>
+</section>
+',
+            ],
+        ];
+    }
+
+    /**
+     * @dataProvider providerConvertDocbookToHtmlEditWithEznoNamespace
+     */
+    public function testConvertDocbookToHtmlEditWithEznoNamespace(string $input, string $expectedOutput): void
+    {
+        $xmlDocument = new DOMDocument();
+        $xmlDocument->loadXML($input);
+
+        $eznoNamespaceConverter = new EzNoNamespace();
+        $xsltConverter = new Xslt(
+            __DIR__ . '/../../../../src/bundle/Resources/richtext/stylesheets/docbook/xhtml5/edit/xhtml5.xsl',
+            [
+                [
+                    'path' => __DIR__ . '/../../../../src/bundle/Resources/richtext/stylesheets/docbook/xhtml5/edit/core.xsl',
+                    'priority' => 100,
+                ],
+            ]
+        );
+
+        $aggregate = new Aggregate([$eznoNamespaceConverter, $xsltConverter]);
+
+        $output = $aggregate->convert($xmlDocument);
+
+        $expectedOutputDocument = new DOMDocument();
+        $expectedOutputDocument->loadXML($expectedOutput);
+        $this->assertEquals($expectedOutputDocument, $output, 'Xml is not converted as expected');
+    }
+
+    public function providerConvertDocbookToHtmlOutputWithEznoNamespace(): array
+    {
+        return [
+            [
+                '<?xml version="1.0" encoding="UTF-8"?>
+<section xmlns="http://docbook.org/ns/docbook" xmlns:ezcustom="http://ez.no/xmlns/ezpublish/docbook/custom" xmlns:ezxhtml="http://ez.no/xmlns/ezpublish/docbook/xhtml" xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0-variant ezpublish-1.0">
+    <para ezxhtml:class="custom_class">
+        This is some text in custom_class with
+        <emphasis>something in bold</emphasis>
+        and the end.
+    </para>
+</section>
+',
+                '<?xml version="1.0" encoding="UTF-8"?>
+<section xmlns="http://ibexa.co/namespaces/ezpublish5/xhtml5">
+    <p class="custom_class">
+        This is some text in custom_class with
+        <em>something in bold</em>
+        and the end.
+    </p>
+</section>
+',
+            ],
+        ];
+    }
+
+    /**
+     * @dataProvider providerConvertDocbookToHtmlOutputWithEznoNamespace
+     */
+    public function testConvertDocbookToHtmlOutputWithEznoNamespace(string $input, string $expectedOutput): void
+    {
+        $xmlDocument = new DOMDocument();
+        $xmlDocument->loadXML($input);
+
+        $eznoNamespaceConverter = new EzNoNamespace();
+        $xsltConverter = new Xslt(
+            __DIR__ . '/../../../../src/bundle/Resources/richtext/stylesheets/docbook/xhtml5/output/xhtml5.xsl',
+            [
+                [
+                    'path' => __DIR__ . '/../../../../src/bundle/Resources/richtext/stylesheets/docbook/xhtml5/output/core.xsl',
+                    'priority' => 100,
+                ],
+            ]
+        );
+
+        $aggregate = new Aggregate([$eznoNamespaceConverter, $xsltConverter]);
+
+        $output = $aggregate->convert($xmlDocument);
+
+        $expectedOutputDocument = new DOMDocument();
+        $expectedOutputDocument->loadXML($expectedOutput);
+        $this->assertEquals($expectedOutputDocument, $output, 'Xml is not converted as expected');
+    }
 }
 
 class_alias(AggregateTest::class, 'EzSystems\Tests\EzPlatformRichText\RichText\Converter\AggregateTest');