An all seeing debugger for your web app

We're building Nut, a chat API for explaining problems in your app. Nut records your app to capture and later analyze the billions of things that happened while it ran, then tells you the root cause. Take the actual work out of figuring out most bugs. 

Try Nut.new ->

Trusted by top engineering teams

Introducing Nut.new

Crack the toughest nuts (bugs)

Nut works especially well with AI code writers. AIs are lousy at debugging problems in code they've written. The basic issue is a lack of context: people use devtools to understand their app, but AIs struggle here. Nut gives AIs the clear explanations they need to fix bugs reliably.

For now we're focusing on Nut.new, a no-code tool in the mold of Bolt, v0, and Lovable. You can build complete apps from scratch by prompting the AI, and call the Nut API to get past the points where other tools get stuck. Nut.new is free to use lightly, and in unlimited amounts through our early adopter program or with your own Anthropic API key.

Nut uses our Chromium-based deterministic browser recorder. The browser captures just enough data while your app is running that it can be replayed later and behave exactly the same. This behavior is queried like a database and processed with advanced techniques such as dataflow and control dependency analysis to get to the underlying cause of any problem in the recording.

Try Nut.new ->

See Nut in action

The Map UI went blank and after five failed attempts, bolt gives up.

The search icon was too small, but v0 could not figure out how to make it larger.

The settings page did not work and Claude 3.7 Sonnet could not figure out what was failing.

The contact book responsive mode went blank and Cursor could not identify the problem.

Searching causes the UI triggers an infinite render because of a missing useCallback.

The Map UI went blank and after five failed attempts, bolt gives up.

Map goes blank

The Map UI went blank and after five failed attempts, bolt gives up.

The tiny search icon

The search icon was too small, but v0 could not figure out how to make it larger.

Broken settings page

The settings page did not work and Claude 3.7 Sonnet could not figure out what was failing.

Unresponsive contact pane

The contact book responsive mode went blank and Cursor could not identify the problem.

Infinite render loop

Searching causes the UI triggers an infinite render because of a missing useCallback.

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Become an early adopter

Nut is early in development. We're offering unlimited free access to Nut.new for early adopters who can give us feedback we'll use to improve Nut. Reach us at hi@replay.io or fill out our contact form to join our early adopter program.

Say goodbye to “works on my machine”

Replay is the first deterministic browser. Once a bug or flaky test is captured, anyone can inspect it with Browser DevTools without having to replicate it locally.

Add console logs in your code with a single click with messages that “automagically” appear in the Console. You’ll love how fast the feedback loop is.

Replay’s built in test timeline helps you inspect test step details and jump from test step actions into your application’s React event handlers.

Bugs can appear at any point in time. Replay’s React panel helps you find the component with first visible issues, inspect its props, and work backwards to the root cause.

The majority of E2E test failures are caused by backend issues. Replay’s Network monitor helps you find the bad request and inspect the application state at the time.

Add console logs in your code with a single click with messages that “automagically” appear in the Console. You’ll love how fast the feedback loop is.

Debug with instant console logs.

Add console logs in your code with a single click with messages that “automagically” appear in the Console. You’ll love how fast the feedback loop is.

Fix flaky Cypress + Playwright tests.

Replay’s built in test timeline helps you inspect test step details and jump from test step actions into your application’s React event handlers.

Inspect React components

Bugs can appear at any point in time. Replay’s React panel helps you find the component with first visible issues, inspect its props, and work backwards to the root cause.

View network requests

The majority of E2E test failures are caused by backend issues. Replay’s Network monitor helps you find the bad request and inspect the application state at the time.

Battle tested.

Replay helps some of the largest companies record their E2E tests at scale and verify the correctness of mission critical software.

Chromium browser: Most folks assume that Replay is a JS library, but you can't record and replay the browser without teaching Chrome a couple of tricks.
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Shockingly fast: You'd think that a lossless recorder would be painstakingly slow, but Replay’s runtime recorder is comparable to recording a video.
Seamless setup: Because Replay is just a browser, you can drop it into your existing test runner + CI environment and beginning debugging runs in minutes.
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Supports all test runners: Replay works with all browser automation tools, but has built-in support for Playwright and Cypress’s test panel.
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