Compatibility · NextToolbar

Feature matrix

Feature	Next 15	Next 16	Next 16 + `requestInsights`
HTTP status (load and client navigation)	✓	✓	✓
Route pattern	heuristic	heuristic	exact
Render mode (Static / Dynamic / Static?)	✓	✓	✓
no-store correction of render mode	—	—	✓
TTFB / navigation time	✓	✓	✓
Server render time	—	—	✓
Server fetches and cache outcome	—	—	✓
Server errors	—	—	✓
Client errors	✓	✓	✓
Request profiler	—	—	✓
`basePath` / `assetPrefix`	✓	✓	✓

"Heuristic" route patterns are rebuilt from usePathname() and useParams(). They're right in almost every case; a param whose value equals a later static segment (e.g. /blog/blog) can be mislabeled.

Tested versions

Version	How
Next 16.3.6	Full test in the browser
Next 15.5.26	Full test in the browser
Next 15.0.8	Reviewed from source (message format), not run

React 19 is required (it's what the App Router uses on Next 15+).

What differs between Next versions

NextToolbar reads Next's internal dev HMR socket, whose shape changed between versions. The toolbar handles all of them:

	15.0	15.5	16.x
Socket path	`/_next/webpack-hmr`	`/_next/webpack-hmr`	`/_next/hmr`
Message field	`action`	`action`	`type`
Static data message	`appIsrManifest`	`isrManifest`	`isrManifest`
Dynamic routes in it	absent	absent	`false`
Request insights	—	—	`requestInsightsUpdate`

Internal API

These are internal, undocumented Next.js messages. A future Next version can change them; when that happens the affected segments show ? instead of breaking the page.

Cache Components

With cacheComponents enabled (Next 16), Next doesn't send static/dynamic data, so the render-mode badge shows ?. Everything else works.

Browsers

Browser	Notes
Chrome, Edge, Firefox	Full support
Safari	No `responseStatus` in the Performance API, so the status shows `—`. Everything else works.

TypeScript

Next 15 can't load next.config.ts with TypeScript 7 (the native compiler has no JavaScript API). Use TypeScript 6 with Next 15, or Next 16.2.11+ for TypeScript 7. This affects your app, not the toolbar.