'Took longer than 30s to boot': Bolt.new WebContainer won't start (or the preview is blank)

Bolt.new Easy 5-15 minutes Last verified Jul 17, 2026

The fix Switch to Chrome or another Chromium browser and retry in an Incognito window; boot failures almost always trace to non-Chromium browsers, ad blockers, VPNs, or antivirus filtering. For out-of-memory errors, close other Bolt and StackBlitz tabs. A blank preview usually means your app crashed at runtime: read the DevTools console, not the spinner.

Symptoms

A spinner that never resolves when the project loads
An error banner that the WebContainer failed to initialize or 'took longer than 30s to boot'
An out-of-memory error
A white or grey preview screen right after an edit

Why it happens

Your whole dev environment runs in the browser tab

Bolt runs Node.js and the dev server inside a WebContainer in your tab, using your machine's memory and requiring modern Chromium APIs. Anything that starves or blocks the tab kills the boot.

Browser and network interference

Non-Chromium browsers, interfering extensions (especially ad blockers), VPNs breaking WebSocket connections, and antivirus filtering are the standard boot killers.

Out of memory

Multiple Bolt or StackBlitz projects and heavy tabs open at once exhaust the memory the WebContainer needs.

A blank preview is a runtime crash, not a boot failure

The dev server started, but the app crashed at runtime (a missing import, a throwing component, a bad env var) and the dev server swallowed the error.

How to fix it

Use a Chromium browserBolt's WebContainer requires modern Chromium APIs. Use Chrome, Edge, Brave, or Arc; other browsers are not reliable for WebContainers, and switching is the single highest-yield fix.
Test in an Incognito window to isolate extensionsOpen bolt.new in Incognito. If the project boots there, an extension is interfering; re-enable them one by one to find the culprit. Ad blockers are the usual offender.
Disable your VPN and whitelist Bolt in antivirusVPNs can break the WebSocket connections the WebContainer depends on, so disable yours and retry. If you see 403 or 404 errors, whitelist bolt.new and stackblitz.io in your antivirus or firewall.
Fix out-of-memory by shedding loadClose other Bolt and StackBlitz tabs and heavy apps, refresh, and restart the machine if needed. Keep only one project open at a time; the WebContainer runs on your machine's memory, not Bolt's servers.
Debug a blank preview like the crash it isOpen the browser DevTools console, copy the exact red error, and paste it into Bolt as a targeted fix prompt. Also run npm run build in Bolt's terminal, because build output shows errors the dev server hides.
Hard-reload and restore as a last resortIf nothing else works, hard-reload with Ctrl/Cmd+Shift+R and restore the last working version from Version History.

How to prevent it

Do Bolt work in Chrome or another Chromium browser, with bolt.new excluded from your ad blocker.
Keep one Bolt project open at a time; WebContainers use your machine's memory.
Whitelist bolt.new and stackblitz.io in antivirus and firewall before it bites you.
When a preview goes blank after an edit, go straight to the DevTools console instead of re-prompting blind.
Run npm run build occasionally; it surfaces errors the dev server hides.

Frequently asked questions

What does 'took longer than 30s to boot' mean in bolt.new?

It means the WebContainer, the in-browser environment that runs your project's Node.js dev server, failed to initialize. The usual causes are a non-Chromium browser, an interfering extension such as an ad blocker, a VPN breaking WebSocket connections, antivirus filtering, or the machine running out of memory. Switching to Chrome and testing in Incognito isolates most of them in a couple of minutes.

Why is my bolt.new preview blank with no error?

A blank preview in bolt.new usually means the dev server started fine but your app crashed at runtime, from something like a missing import, a throwing component, or a bad environment variable, and the dev server swallowed the error. Open the browser DevTools console for the real red error, and run npm run build in Bolt's terminal since build output surfaces errors the dev server hides.

Which browsers work with bolt.new?

Bolt.new is reliable in Chromium browsers: Chrome, Edge, Brave, and Arc. The WebContainer that runs your dev environment depends on modern Chromium APIs, so other browsers are not reliable for it. If Bolt fails to boot, switching to Chrome is the first fix to try.

Can a VPN or antivirus break bolt.new?

Yes. VPNs can break the WebSocket connections the WebContainer depends on, and antivirus filtering can block requests, showing up as boot failures or 403 and 404 errors. Disable the VPN to test, and whitelist bolt.new and stackblitz.io in your antivirus or firewall.

Sources

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