Does Loki Support Firefox or Only Chrome for Website Screenshots?
Loki documents Chrome targets for Storybook screenshots, not Firefox. Here’s what that means, what Firefox can do on its own, and what to use instead.
Short answer: Loki’s documented browser targets for Storybook visual regression screenshots are Chrome-based. Firefox is not listed as a supported Loki target. The documented platform list also includes iOS simulator and Android emulator, so “only Chrome” is accurate for the listed desktop browser targets, but not for every Loki execution target. The documentation does not establish that every custom or third-party renderer is technically impossible.
This article is about Loki, the Storybook visual regression testing project, not other tools that share the Loki name. The project describes its purpose as making it easy to test a Storybook project for visual regressions.
What Loki documents as supported
The Loki README lists these platforms:
| Platform | What it means for screenshots |
|---|---|
| Chrome in Docker | A Chrome-based environment for capturing Storybook stories; the Loki project recommends this option. |
| Chrome in AWS Lambda | A Chrome-based target running in AWS Lambda. |
| Local Chrome | A Chrome application on the machine running Loki. |
| iOS simulator | A mobile simulator target, not a desktop Firefox browser target. |
| Android emulator | A mobile emulator target, not a desktop Firefox browser target. |
Firefox does not appear in that documented supported-platform list. The careful conclusion is therefore that Loki documents Chrome browser targets and does not list Firefox as a supported target. That is different from proving that no custom integration could ever be built or that the project could never add Firefox support.
Firefox screenshots are a separate capability
Firefox has its own screenshot features. Mozilla documents ways to capture a full page or a visible area, and developer tools can capture page elements. Those features operate within Firefox. They do not mean Loki can launch Firefox as its automated browser for Storybook visual regression tests.
Use the distinction that matches your task:
- Need a manual Firefox screenshot? Use Firefox’s built-in screenshot workflow or developer tools.
- Need automated Storybook visual regression checks with Loki? Choose one of the documented Loki targets and check the repository’s current configuration and prerequisites for your Loki version.
- Need a screenshot of a deployed website rather than a Storybook story? Use a browser screenshot workflow or a screenshot API; Loki is specifically for Storybook visual regression testing.
How to check your Loki setup
- Confirm which Loki project you mean. This answer concerns
oblador/loki, the Storybook visual regression tool. - Read the supported-platform list for your installed version. Start with the Loki repository README, including its setup prerequisites and configuration documentation.
- Look for a documented Firefox target before configuring one. Do not infer Loki compatibility from Firefox’s own screenshot tools or from a browser being installed on the same machine.
- If Firefox rendering is a requirement, decide how to run that check separately. Evaluate a visual testing workflow that documents Firefox support, or create a custom workflow only after verifying that its capture and comparison steps work for your Storybook setup.
- Keep browser environments consistent. Visual comparisons can vary with browser engine, fonts, viewport, device scale, operating system, and timing. Compare runs made with the same environment when you want meaningful regression results.
What to do if you specifically need Firefox rendering
The available project documentation does not list Firefox as a Loki target. If Firefox-specific rendering is a release requirement, treat that as a separate compatibility check rather than assuming Loki will cover it. Inspect the current Loki configuration and repository for any newer documented target, then choose a Firefox-capable test runner if no supported option is listed.
For a custom setup, keep the responsibilities explicit: load the Storybook story, select the Firefox browser runtime, capture at a fixed viewport and device scale, wait for fonts and relevant assets, and compare the output against a baseline created with the same browser environment. This is a general workflow outline, not a claim that Loki provides those Firefox controls.
Common misunderstandings and troubleshooting
| Symptom or assumption | Why it happens | What to do |
|---|---|---|
| “Firefox is installed, so Loki should use it.” | A local browser installation does not make it a documented Loki target. | Use a platform listed by Loki, or select a separate workflow that explicitly supports Firefox. |
| “Firefox can take screenshots, so Loki supports Firefox.” | Native browser screenshots and automated Storybook visual regression targets are different capabilities. | Use Firefox’s own tools for direct captures; check Loki’s supported-platform documentation for Loki automation. |
| “Loki only supports Chrome, with no other platforms.” | This overlooks the documented iOS simulator and Android emulator targets. | Say that Loki’s documented desktop browser targets are Chrome-based, alongside its mobile simulator and emulator targets. |
| A screenshot differs between local and CI runs. | The browser target or rendering environment may differ, including fonts, viewport, scale, or timing. | Run comparisons with a consistent documented target and matching capture conditions. |
| A team cannot find a Firefox configuration option. | Firefox is absent from the documented supported-platform list. | Check the current README and installed version. Avoid relying on an undocumented option for a required check. |
Performance, reliability, and cost considerations
The reviewed Loki and Mozilla documentation does not provide comparable performance benchmarks or cost figures for Firefox versus Chrome screenshots. Avoid choosing a target based on an assumed speed or price advantage.
For reliable visual regression results, pin the rendering environment as much as your workflow allows and keep the browser, operating system, fonts, viewport, device scale, and asset readiness consistent across baseline and comparison runs. If you add a separate Firefox workflow, maintain a Firefox-specific baseline: screenshots from different browser engines are not interchangeable pixel-for-pixel.
For ordinary screenshots of a live website, a managed screenshot API can avoid maintaining a browser runtime. ScreenshotNeo is a website screenshot API and MCP server; it is not a Loki Firefox target and should not be presented as one.
Or skip the browser setup
For a screenshot of a public website, ScreenshotNeo takes a screenshot with one GET request. This is separate from running Loki against Storybook.
See the ScreenshotNeo API documentation for the available parameters. This cURL request saves a WebP screenshot of Stripe:
curl -G "https://api.screenshotneo.com/v1/shot" -d access_key=YOUR_API_KEY --data-urlencode url=https://stripe.com -o shot.webpPython:
import requests
r = requests.get(
"https://api.screenshotneo.com/v1/shot",
params={"access_key": "YOUR_API_KEY", "url": "https://stripe.com"},
timeout=90,
)
r.raise_for_status()
open("shot.webp", "wb").write(r.content)Node.js:
const q = new URLSearchParams({
access_key: 'YOUR_API_KEY',
url: 'https://stripe.com'
});
const res = await fetch(`https://api.screenshotneo.com/v1/shot?${q}`);
if (!res.ok) throw new Error(`Screenshot request failed: ${res.status}`);
await Bun.write('shot.webp', res);ScreenshotNeo accepts consent banners like a visitor and removes more than 60 known consent platforms, newsletter popups, and chat widgets before capture; each cleanup step can be turned off. Bot checks, blank pages, failed loads, timeouts, and cache hits are not billed, and response headers identify the page verdict and billing status. Its MCP server offers take_screenshot, get_page_info, and capture_pdf for AI agents. The free plan includes 1,000 screenshots per month with no card; paid plans start at $5 for 3,000 screenshots. Every feature is available on every plan.
Sign up free for 1,000 screenshots a month, with no card required.
FAQ
Does Loki explicitly say Firefox is impossible to use?
No. The documented platform list does not include Firefox. That supports saying Firefox is not a documented Loki target, but it does not prove every custom or third-party renderer is impossible.
Does Loki support mobile screenshots?
The documented platforms include an iOS simulator and Android emulator, in addition to its Chrome targets.
Can Firefox take a full-page screenshot?
Yes. Mozilla documents Firefox screenshot workflows, including full-page capture. This is a Firefox browser feature, not evidence of Loki support.
Can I use ScreenshotNeo to run Loki tests?
No. ScreenshotNeo captures website screenshots and PDFs through an API or MCP server. Loki is a Storybook visual regression tool; the ScreenshotNeo call above is for capturing a website URL.
Sources
- Loki repository README — project purpose, supported platforms, and setup documentation.
- Loki project website — project description and recommended Chrome in Docker platform.
- Mozilla Support: Firefox Screenshots — Firefox’s built-in screenshot capability.
- MDN: Screenshot tool — developer-tool screenshot workflow.
