Browser Support
DontBreak runs your tests in real browser engines — Chromium and Firefox — on both desktop and mobile viewports. This page is the definitive support matrix: which browsers run, what the viewports are, and which actions are limited on which platforms.
Support matrix
| Desktop | Mobile | |
|---|---|---|
| Chrome (Chromium) | Supported | Supported |
| Firefox | Supported | Supported (touch emulation) |
You enable any combination of these per test in Test Settings → Test Platforms, and each enabled combination runs as its own session — and counts as one run against your quota. See Browsers & Devices for configuring combinations.
Testing Chromium covers most browsers
We test on engines, not brand names — and Chromium is the engine behind the large majority of browsers people actually use. A passing Chromium run is representative of every browser built on it, including:
- Google Chrome
- Microsoft Edge
- Brave
- Opera
- Arc
- Vivaldi
- Samsung Internet (on mobile)
They share Chromium's rendering (Blink) and JavaScript (V8) engines, so your test exercises the same layout and behavior those users get — testing "Chrome" effectively covers all of them. Firefox (Gecko) is the meaningful second engine, which is why it's offered alongside Chromium for true cross-engine coverage. The only major engine not covered is Safari/WebKit (below).
Safari/WebKit isn't supported yet
Safari/WebKit is the one major engine the matrix above doesn't cover. It's a smaller slice of real-world traffic, and supporting it adds meaningful infrastructure overhead for relatively little additional coverage — so it isn't part of the run matrix today. This is a deliberate scoping choice, not a permanent limitation: we may add WebKit down the line, but there's no timeline. Until then, treat this page as the source of truth — if a stub, sales page, or older doc mentions Safari, tests run on Chromium and Firefox only.
Viewports
| Device type | Viewport | Notes |
|---|---|---|
| Desktop | 1280 × 1024 | Standard desktop session |
| Mobile | 375 × 812 | Mobile user agent, touch enabled |
Mobile runs use a phone-sized viewport with a mobile user agent and touch input, and they execute your test's mobile steps — a separate step list from the desktop version. On Chromium, mobile emulation is full-fidelity (mobile mode plus real touch dispatch). On Firefox, mobile runs use touch events and a mobile user agent, which covers responsive layouts and mobile-targeted CSS, but without Chromium's deeper device emulation.
Firefox mobile gesture limitations
Three gesture actions need real-input touch dispatch, which is only available on Chromium:
- Swipe
- Long Press
- Pull to Refresh
These run normally on Chrome Mobile but are skipped on Firefox Mobile. The test editor warns you when a test with these steps has Firefox Mobile enabled.
Two actions are desktop-only and are skipped on mobile runs:
- Right Click
- Hover
What "Skipped" means
When a step can't run on the current platform, DontBreak doesn't fail the run — the step is marked Skipped in the report, with a short message explaining why, and execution continues with the next step. Skipped steps consume no extra runs and don't affect the pass/fail outcome.
This means it's safe to author one test with platform-specific steps: a Swipe step simply skips on desktop and Firefox Mobile runs, while a Hover step skips on mobile.
Cross-browser differences
Chromium and Firefox render text and some CSS slightly differently. DontBreak's visual matching tolerates normal rendering variation, but if a step fails on only one browser:
- Check the step's Debug match info in the report — the confidence score shows how close the match was. See Common Errors.
- For genuinely browser-sensitive targets, the techniques in Test Reliability (larger target areas, masks, DOM locators) make steps engine-agnostic.
A failure on one browser but not the other can also be a real bug on your site — that's exactly what cross-browser testing is for.
Related
- Browsers & Devices — enabling combinations and quota math
- Actions: Interactions — the full action catalog, including mobile gestures
- Test Settings — per-test platform configuration