# Sudden 404 Error in Firebase Studio Project (IDX)

**URL:** <https://community.firebasestudio.dev/t/sudden-404-error-in-firebase-studio-project-idx/18783>\
**Category:** Previews\
**Tags:** troubleshooting\
**Created:** [September 4, 2025, 4:55pm UTC](https://community.firebasestudio.dev/t/sudden-404-error-in-firebase-studio-project-idx/18783 "2025-09-04T16:55:32Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Abdul\_Rehman2](https://sea2.discourse-cdn.com/flex002/user_avatar/community.firebasestudio.dev/abdul_rehman2/32/4458_2.png) [@Abdul\_Rehman2](https://community.firebasestudio.dev/u/Abdul_Rehman2)\
**Post date:** [September 4, 2025, 4:55pm UTC](https://community.firebasestudio.dev/t/sudden-404-error-in-firebase-studio-project-idx/18783/1 "2025-09-04T16:55:33Z")

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My Firebase Studio project was running perfectly on IDX. Suddenly, I didn’t make any major changes except touching a JSON file, and now my entire app has stopped working. I also downgraded my Next.js version from 15 to 14.2.5, but the issue persists.it gives a 404 error. My folder structure is correct, and I am using the `app` route properly. when i test this app on firebase preview link.

Is anyone else experiencing issues, or is there an update running on IDX that might be causing this?

Thanks for any guidance.

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**Author:** ![Antonio\_Scott](https://sea2.discourse-cdn.com/flex002/user_avatar/community.firebasestudio.dev/antonio_scott/32/9291_2.png) [@Antonio\_Scott](https://community.firebasestudio.dev/u/Antonio_Scott)\
**Post date:** [October 5, 2025, 1:12pm UTC](https://community.firebasestudio.dev/t/sudden-404-error-in-firebase-studio-project-idx/18783/2 "2025-10-05T13:12:40Z")

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Hey there 👋 — this type of 404 in Firebase Studio’s preview often isn’t about your routing code itself, but about how the **preview environment** is building and interpreting your routes.

A few things that can cause this suddenly, even if your app structure looks fine:

**1. Build manifest drift**

- When a config or JSON file changes, or when you switch framework versions (like from Next.js 15 → 14), the build pipeline may silently regenerate or drop routing entries.

- That can cause the deployed preview to “lose” routes, even though they work locally.

**2. Stale or mismatched preview cache**

- Firebase Studio sometimes holds onto a cached preview build or routes manifest.

- If it doesn’t rebuild cleanly, you may end up serving an older artifact that still references outdated routes.

**Try this clean-reset sequence:**

1. Delete your local `.next`, `.firebase`, and `node_modules` folders.

2. Reinstall dependencies and rebuild:

3. Trigger a **fresh preview deploy** , not an incremental one — make sure caching is disabled or cleared.

4. Double-check your `next.config.js` and `firebase.json` rewrites to ensure nothing was dropped.

If your preview build logs mention “route not found” or “missing manifest entry,” that’s the confirmation — the environment is serving a stale or incomplete bundle. Once the cache is flushed and rebuilt from scratch, routes usually come back immediately.

Hope this helps narrow it down — these 404s are rarely random, they’re almost always linked to how the preview environment cached your routing manifest.