diff --git a/.changeset/neaps-esm-only.md b/.changeset/neaps-esm-only.md
new file mode 100644
index 0000000..419c569
--- /dev/null
+++ b/.changeset/neaps-esm-only.md
@@ -0,0 +1,10 @@
+---
+"neaps": minor
+"@neaps/tide-predictor": minor
+"@neaps/react": minor
+---
+
+Drop the CommonJS builds; all neaps packages are now ESM-only. The CJS entries
+can't survive their dependencies going ESM-only, since they load them with
+`require()`. CommonJS consumers on Node 20.19+ / 22.12+ can still `require()`
+these packages via Node's `require(esm)` support.
diff --git a/packages/neaps/package.json b/packages/neaps/package.json
index 7bd30e3..508c0c6 100644
--- a/packages/neaps/package.json
+++ b/packages/neaps/package.json
@@ -18,12 +18,11 @@
   "license": "MIT",
   "author": "Brandon Keepers <brandon@openwaters.io>",
   "type": "module",
-  "main": "dist/index.cjs",
+  "main": "dist/index.js",
   "exports": {
     ".": {
       "types": "./dist/index.d.ts",
-      "import": "./dist/index.js",
-      "require": "./dist/index.cjs"
+      "import": "./dist/index.js"
     }
   },
   "files": [
diff --git a/packages/react/package.json b/packages/react/package.json
index 0a5bc88..f9262ff 100644
--- a/packages/react/package.json
+++ b/packages/react/package.json
@@ -19,12 +19,11 @@
   "license": "MIT",
   "author": "Brandon Keepers <brandon@openwaters.io>",
   "type": "module",
-  "main": "dist/index.cjs",
+  "main": "dist/index.js",
   "exports": {
     ".": {
       "types": "./dist/index.d.ts",
-      "import": "./dist/index.js",
-      "require": "./dist/index.cjs"
+      "import": "./dist/index.js"
     },
     "./styles.css": "./dist/styles.css"
   },
diff --git a/packages/react/tsdown.config.ts b/packages/react/tsdown.config.ts
index deb3ab8..4b3ef73 100644
--- a/packages/react/tsdown.config.ts
+++ b/packages/react/tsdown.config.ts
@@ -3,7 +3,7 @@ import { defineConfig } from "tsdown";
 export default defineConfig({
   entry: ["./src/index.ts"],
   dts: true,
-  format: ["cjs", "esm"],
+  format: ["esm"],
   sourcemap: true,
   target: "es2020",
   platform: "browser",
diff --git a/packages/tide-predictor/package.json b/packages/tide-predictor/package.json
index 75be49d..a2fbcc7 100644
--- a/packages/tide-predictor/package.json
+++ b/packages/tide-predictor/package.json
@@ -10,12 +10,11 @@
   "author": "Kevin Miller <keveemiller@gmail.com>",
   "license": "MIT",
   "type": "module",
-  "main": "dist/index.cjs",
+  "main": "dist/index.js",
   "exports": {
     ".": {
       "types": "./dist/index.d.ts",
-      "import": "./dist/index.js",
-      "require": "./dist/index.cjs"
+      "import": "./dist/index.js"
     }
   },
   "files": [
diff --git a/tsdown.config.js b/tsdown.config.js
index 5f71df8..2ad13f7 100644
--- a/tsdown.config.js
+++ b/tsdown.config.js
@@ -3,7 +3,7 @@ import { defineConfig } from "tsdown";
 export default defineConfig({
   entry: ["./src/index.ts"],
   dts: true,
-  format: ["cjs", "esm"],
+  format: ["esm"],
   sourcemap: true,
   declarationMap: true,
   target: "es2020",