tweak blog: mock APIs, debug HTTP and test frontends

The happy path gets tested every time someone opens the app. The error paths get tested when production breaks. That is backwards: an error screen is the one screen a user sees when they are already frustrated, and it is usually the least reviewed code in the project. The reason is simple: errors are hard to produce on demand. The backend works, so you cannot see what happens when it does not.

This guide lists the failures worth testing, what a good UI does for each, and how to produce every one of them in the browser without changing a line of backend code.

You want the next request to go out a little differently. A bigger quantity, an expired token, someone else's id, a field the backend does not support yet. Not forever, just this once, to see what happens.

That is a request breakpoint: stop the request in flight, edit it, let it go. Desktop proxies have done this for twenty years, but they ask you to reroute your traffic and trust a certificate first. This guide shows how to do it from inside the page with tweak's Pause & Edit (previously called Edit before send), which use cases it covers, and how it compares, feature and price, with Charles, Fiddler, Proxyman, Burp Suite and the free tools.

On July 10, 2026, Google and Microsoft pulled ModHeader from the Chrome Web Store and Edge Add-ons. Roughly 1.6 million installs, gone in a few days, after dormant data-collection code was found buried in the extension. If you were one of those users, or you're just re-evaluating what you trust with request and header access, here's what happened, what tweak does differently, and how to move your header rules and profiles over. Still choosing a replacement? ModHeader alternatives compares the options.

Four things shipped in v9.0.0. On their own, each one saves you a few clicks. Put together, they change how a debugging session actually feels: fewer detours, less waiting, more of your attention staying on the problem in front of you.

We're always looking for new ways to improve our effectiveness as frontend developers. We want to pick the right tools to get the job done. We want to have a fully equipped browser, to troubleshoot any tricky bug that comes our way.

Browser extensions have been around for a while, making their way into our development workflow in many different shapes. We can think of extensions as development companions.

In this article, we would like to share a few of them that, in our opinion, provide valuable assistance for frontend developers.

Sooner or later every frontend team builds a screen against an API that does not exist yet, is down, or cannot be made to return the case you need. There are two broad ways to fake it in the browser: put the mocks inside your app with a library like Mock Service Worker (MSW), or put them outside your app with a browser extension. They solve the same problem from opposite ends, and picking the wrong one costs you either setup time or test coverage.

If you're debugging HTTP requests and network issues, you've likely considered both tweak and Proxyman. Both tools let you intercept, inspect, and modify network traffic, but they approach the problem from different angles. tweak is a lightweight browser extension; Proxyman is a full-featured desktop proxy application. Understanding their differences will help you pick the right one for your workflow.

If you've been searching for a way to mock HTTP requests in your browser, you've likely come across both tweak and Requestly. Both tools let you intercept and modify network requests without touching your backend, but they approach the problem differently. This post breaks down what each tool does well and when you should reach for one over the other.

Another year, another existential question: will AI tools/agents or AI browsers replace browser extensions? Spoiler alert: not yet. But let's talk about what actually happened in 2025.

It's possible to pin a Chrome extension in the Chrome browser simply following the steps:

1. Open the Chrome browser.
2. Click on the "puzzle piece" icon in the top right corner of the browser.
3. Locate the extension you want to pin.
4. Click on the "pin" icon next to the extension you want to pin.

Below an imagine and a short clip to illustrate the steps.