diff --git a/.changeset/beige-falcons-mate.md b/.changeset/beige-falcons-mate.md
new file mode 100644
index 000000000..641aa9c43
--- /dev/null
+++ b/.changeset/beige-falcons-mate.md
@@ -0,0 +1,13 @@
+---
+"ilib-lint-python-gnu": patch
+"ilib-tools-common": patch
+"ilib-lint-common": patch
+"ilib-lint-python": patch
+"ilib-data-utils": patch
+"ilib-lint-react": patch
+"ilib-assemble": patch
+"ilib-lint": patch
+"tmxtool": patch
+---
+
+Unified package entrypoint definitions. This should help resolve edge cases where older packages (like Jest 26) were unable to correctly load some of them.
diff --git a/packages/ilib-assemble/package.json b/packages/ilib-assemble/package.json
index 84bed8c0d..e077d3cab 100644
--- a/packages/ilib-assemble/package.json
+++ b/packages/ilib-assemble/package.json
@@ -1,8 +1,9 @@
 {
     "name": "ilib-assemble",
     "version": "1.3.1",
-    "main": "./src/index.js",
     "type": "module",
+    "main": "./src/index.js",
+    "module": "./src/index.js",
     "bin": {
         "ilib-assemble": "./src/index.js",
         "ilib-assemble.bat": "./ilib-assemble.bat"
diff --git a/packages/ilib-data-utils/package.json b/packages/ilib-data-utils/package.json
index d603945f7..6ff429a6c 100644
--- a/packages/ilib-data-utils/package.json
+++ b/packages/ilib-data-utils/package.json
@@ -3,6 +3,12 @@
     "version": "1.2.2",
     "main": "./lib/index.js",
     "module": "./src/index.js",
+    "exports": {
+        ".": {
+            "require": "./lib/index.js",
+            "import": "./src/index.js"
+        }
+    },
     "description": "Utilities used to generate locale data for ilib packages",
     "keywords": [
         "internationalization",
diff --git a/packages/ilib-lint-common/package.json b/packages/ilib-lint-common/package.json
index 19a7edc45..ed903f73c 100644
--- a/packages/ilib-lint-common/package.json
+++ b/packages/ilib-lint-common/package.json
@@ -1,8 +1,9 @@
 {
     "name": "ilib-lint-common",
     "version": "3.1.1",
-    "module": "./src/index.js",
     "type": "module",
+    "main": "./src/index.js",
+    "module": "./src/index.js",
     "exports": {
         ".": {
             "import": "./src/index.js"
diff --git a/packages/ilib-lint-python-gnu/package.json b/packages/ilib-lint-python-gnu/package.json
index e1ab0e89f..fedbab2f4 100644
--- a/packages/ilib-lint-python-gnu/package.json
+++ b/packages/ilib-lint-python-gnu/package.json
@@ -1,13 +1,12 @@
 {
     "name": "ilib-lint-python-gnu",
     "version": "2.0.2",
-    "main": "./src/index.js",
     "type": "module",
+    "main": "./src/index.js",
+    "module": "./src/index.js",
     "exports": {
         ".": {
-            "default": {
-                "default": "./src/index.js"
-            }
+            "import": "./src/index.js"
         },
         "./package.json": "./package.json"
     },
diff --git a/packages/ilib-lint-python/package.json b/packages/ilib-lint-python/package.json
index 2db0e0941..ccba405a2 100644
--- a/packages/ilib-lint-python/package.json
+++ b/packages/ilib-lint-python/package.json
@@ -1,13 +1,12 @@
 {
     "name": "ilib-lint-python",
     "version": "2.0.2",
-    "main": "./src/index.js",
     "type": "module",
+    "main": "./src/index.js",
+    "module": "./src/index.js",
     "exports": {
         ".": {
-            "default": {
-                "default": "./src/index.js"
-            }
+            "import": "./src/index.js"
         },
         "./package.json": "./package.json"
     },
diff --git a/packages/ilib-lint-react/package.json b/packages/ilib-lint-react/package.json
index af2a6d975..3ff4a3f64 100644
--- a/packages/ilib-lint-react/package.json
+++ b/packages/ilib-lint-react/package.json
@@ -1,13 +1,12 @@
 {
     "name": "ilib-lint-react",
     "version": "2.0.2",
-    "main": "./src/index.js",
     "type": "module",
+    "main": "./src/index.js",
+    "module": "./src/index.js",
     "exports": {
         ".": {
-            "default": {
-                "default": "./src/index.js"
-            }
+            "import": "./src/index.js"
         },
         "./package.json": "./package.json"
     },
diff --git a/packages/ilib-lint/package.json b/packages/ilib-lint/package.json
index c13de81e5..291b545d4 100644
--- a/packages/ilib-lint/package.json
+++ b/packages/ilib-lint/package.json
@@ -1,8 +1,9 @@
 {
     "name": "ilib-lint",
     "version": "2.7.1",
-    "module": "./src/index.js",
     "type": "module",
+    "main": "./src/index.js",
+    "module": "./src/index.js",
     "bin": "./src/index.js",
     "description": "A linter for i18n issues for any type of project",
     "keywords": [
diff --git a/packages/ilib-tools-common/package.json b/packages/ilib-tools-common/package.json
index d03d4001b..d55cb1545 100644
--- a/packages/ilib-tools-common/package.json
+++ b/packages/ilib-tools-common/package.json
@@ -1,6 +1,7 @@
 {
     "name": "ilib-tools-common",
     "version": "1.12.1",
+    "main": "./lib/index.js",
     "module": "./src/index.js",
     "exports": {
         ".": {
diff --git a/packages/tmxtool/package.json b/packages/tmxtool/package.json
index ba71439b9..313ac3216 100644
--- a/packages/tmxtool/package.json
+++ b/packages/tmxtool/package.json
@@ -1,8 +1,9 @@
 {
     "name": "tmxtool",
     "version": "1.0.3",
-    "main": "./src/index.js",
     "type": "module",
+    "main": "./src/index.js",
+    "module": "./src/index.js",
     "bin": {
         "tmxtool": "./src/index.js",
         "tmxtool.bat": "./tmxtool.bat"
diff --git a/scripts/check-package-exports.js b/scripts/check-package-exports.js
new file mode 100644
index 000000000..a7c8779a9
--- /dev/null
+++ b/scripts/check-package-exports.js
@@ -0,0 +1,51 @@
+// Usage: node scripts/check-package-exports.js
+// This script checks that all packages have correct entrypoint fields
+
+const fs = require("fs");
+
+const packageFiles = fs
+    .readdirSync("packages")
+    .map((package) => `packages/${package}/package.json`)
+    .filter((file) => fs.existsSync(file));
+for (const path of packageFiles) {
+    console.log(`Processing ${path}`);
+    const data = fs.readFileSync(path, "utf8");
+    const pkg = JSON.parse(data);
+
+    const { main, module } = pkg;
+
+    const type = pkg.type ?? "commonjs";
+
+    // either { exports: { .: { import, require } } } or { exports: { import, require } }
+    const exportsRoot = pkg.exports?.["."] ?? pkg.exports;
+
+    if (!main) {
+        // main should be present regardless of type
+        // because it's the default entry point for a package in Node.js
+        // if type is commonjs, it should point to a commonjs file,
+        // if type is module, it should point to an es module file
+        console.error("No main field found");
+    }
+
+    if (type === "module" && !module) {
+        // module should be present if type is module
+        // this is not officially required, but often used for ESM entry point
+        console.error("Type is module, but no module field found");
+    }
+
+    if (main && module && main !== module && !exportsRoot) {
+        // when both main and module are present and are different,
+        // this means that the package provides both CJS and ESM code;
+        // in this case, per Node documentation, the package should have an exports field
+        // with separate import and require: https://nodejs.org/api/packages.html#conditional-exports
+        console.error("Main and module are different, but no exports field found");
+    }
+
+    if (exportsRoot && (!type || type === "commonjs") && !exportsRoot.require) {
+        console.error("Exports are present and type is commonjs, but no require field found in exports");
+    }
+
+    if (exportsRoot && type === "module" && !exportsRoot.import) {
+        console.error("Exports are present and type is module, but no import field found in exports");
+    }
+}