The Yellow Lab Tools Insider’s Guide
Everything we know about Yellow Lab Tools in one document: what it costs, its grades, getting a refund, getting help and what else to look at. Read it here, or keep a copy.
Yellow Lab Tools
The Insider’s Guide
Free open-source audit of a page's speed and front-end code
Every plan, grade, refund rule and rival among technical SEO tools, read from Yellow Lab Tools’s own pages.
Made by Gaël Métais · checked Oct 23, 2026 · toolgpa.com
Contents
- 01WelcomeWhat it is, who it suits, its grades and the ten things to know first
- 02What it costsEvery plan, the free plan, ways to pay less and how prices have moved
- 03What it doesIts main features, where it runs, what it works with and who makes it
- 04Where it standsIts grades against its category, and whether to keep it or make your own
- 05The alternativesThe tools it is most often weighed against, side by side
- 06Quick answersThe questions people ask about it, each answered in a line or two
- 07About ToolGPAWho made this guide, what else is on the site, and how to cite it
ToolGPA put this guide together from Yellow Lab Tools’s own pages, its app-store listings and our grades. Every fact in it is on Yellow Lab Tools’s page too, where it is kept up to date. Checked Oct 23, 2026.
Part 01 · Overview
Welcome
What it is, who it suits, its grades and the ten things to know first
3.2
GPA, above 81 of the 83 other technical SEO tools we grade
Yellow Lab Tools is a free, GPL-licensed tool by web performance consultant Gaël Métais that loads one page in headless Chrome and scores it for performance and front-end code quality. Each rule gets a grade, the offending files or lines are listed, and the report shows how far the overall score would rise if the issue were fixed. It runs on a public website, as a command-line tool, or on your own server.
To get you started, here are 8 things to know about Yellow Lab Tools, taken from its own pages and our grades.
On the public site you give it a page address and a device type and wait for the report.
- 1
Best for auditing one page's front-end code for free
Yellow Lab Tools loads one page in headless Chrome and grades its JavaScript, CSS, images, fonts and server settings, listing the files at fault and how many points each fix would add.
- 2
It is free
Yellow Lab Tools has no paid plan at all. Entirely free: the public website, the API, the command-line tool and the self-hosted server, with donations through GitHub or Ko-fi.
- 3
It runs on 3 platforms
Web, macOS and Linux.
- 4
Scored page audit
Gives a global score out of 100 and a grade per rule, grouped as network, images, DOM, JavaScript, jQuery, CSS, web fonts and server config.
- 5
Offenders and score gain
Each rule lists the files, selectors or functions at fault and says how many points the global score would gain if it were fixed.
- 6
Device and access settings
Simulates a phone, tablet or desktop, and can send cookies, basic HTTP login details or a proxy, or block and allow chosen domains.
- 7
A 3.2 GPA, above 81 of 83
That is against the other technical SEO tools we grade, on value, the free plan, features, ease of use and platforms.
- 8
Keep it
Yellow Lab Tools is free, so making your own would save you nothing.
Yellow Lab Tools at a glance
- Pricing
- Free
- Free plan
- Yes
- Free trial
- None stated
- Runs on
- Web, macOS, Linux
- Made by
- Gaël Métais
- Category
- Technical SEO & Site Audits
- Our grade
- 3.2 GPA, very good
The report card
Best for auditing one page's front-end code for free
Yellow Lab Tools loads one page in headless Chrome and grades its JavaScript, CSS, images, fonts and server settings, listing the files at fault and how many points each fix would add. It's free, but it tests one address at a time with no site crawl or scheduled monitoring, and runs on the public site can queue behind other people's.
| Subject | Grade | Comment |
|---|---|---|
| Value for money | A | Free under the GPL-2.0 license: the public website, its REST API, the npm command-line tool and the server code. There's no paid plan; the author takes donations through GitHub or Ko-fi. |
| Free plan and trial | A | Every part is free, with no paid tier on record. The catch is the public instance, which processes one run at a time, so a test can wait in a queue. |
| Features | C | A score out of 100 and a grade per rule across network, images, DOM, JavaScript, CSS, fonts and server config, with the offending files listed. It does a one-page front-end audit fully, but that's a smaller job, with no site-wide crawl or monitoring described. |
| Ease of use | B | No rating on record. On the public site you give it a page address and a device type and wait for the report. Running your own copy is another matter: it needs Node.js, documented for Linux and macOS only. |
| Platforms and integrations | B | Web, with a public REST API that returns JSON, plus an npm command-line tool and a server you can run on Mac or Linux. No phone app, and no integrations on record. |
An A is worth 4 points, a B 3, a C 2, a D 1 and an F nothing. The GPA is the average of the five.
Who Yellow Lab Tools is for
- Fits if you're a front-end developer tracing what makes one page heavy or slow
- Works for testing pages on localhost or an intranet through a private copy
Who it is not for
- Skip it if you need a whole site checked, as each run tests one page address
- Not for you if you want ongoing monitoring, since no scheduled tests are described
- Watch out: the public site processes one run at a time, so a test can wait behind others
- Tight if you self-host on Windows, which the author says is untested; Linux and macOS are documented
- Watch out: under GPL-2.0, changes to a hosted copy's code must be published under the same license
Good to know
Good for
- Front-end developers tracing what makes a single page heavy or slow
- Reviewing a page's JavaScript, CSS, images and fonts against good practice
- Testing pages on localhost or behind a firewall with a private instance
Worth knowing
- Each run tests one page address; the documentation describes no site-wide crawl or scheduled monitoring.
- The public instance queues runs and processes one at a time, so a test can wait behind others.
- Self-hosting needs Node.js and is documented for Linux and macOS; the author says Windows is untested.
- Under the GPL-2.0 license, changes to the code of a hosted copy must be published under the same license.
Part 02 · Pricing
What it costs
Every plan, the free plan, ways to pay less and how prices have moved
Free
No paid plan at all
Yellow Lab Tools is free to use.
There's no paid plan; the author takes donations through GitHub or Ko-fi.
Free
$0
The public instance at yellowlab.tools, its REST API, the npm command-line tool and the open-source server.
The free plan
Entirely free: the public website, the API, the command-line tool and the self-hosted server, with donations through GitHub or Ko-fi.
Read from yellowlab.tools on Oct 23, 2026.
Part 03 · Features
What it does
Its main features, where it runs, what it works with and who makes it
3
Places it runs: Web, macOS and Linux
Free open-source audit of a page's speed and front-end code. Here is what it does, as its own site describes it, and what it covers: open source, self-hostable, public API, page speed.
It does a one-page front-end audit fully, but that's a smaller job, with no site-wide crawl or monitoring described.
- Scored page audit
- Gives a global score out of 100 and a grade per rule, grouped as network, images, DOM, JavaScript, jQuery, CSS, web fonts and server config.
- Offenders and score gain
- Each rule lists the files, selectors or functions at fault and says how many points the global score would gain if it were fixed.
- Device and access settings
- Simulates a phone, tablet or desktop, and can send cookies, basic HTTP login details or a proxy, or block and allow chosen domains.
- Public API
- A REST API on yellowlab.tools queues runs, reports their status and returns the full JSON result or parts of it, with CORS allowed.
- Command line and Node module
- Installed from npm, the yellowlabtools command tests a page and prints the result as JSON or XML, with an optional screenshot.
- Private server
- The server code can be installed on your own machine or run from a community Docker image, for testing pages on localhost or an intranet.
Where it runs
- Web
- macOS
- Linux
What it works with
Its own pages name no integrations.
Yellow Lab Tools is made by Gaël Métais.
Part 04 · Standing
Where it stands
Its grades against its category, and whether to keep it or make your own
81/83
Other technical SEO tools it is graded above
Yellow Lab Tools's GPA of 3.2 is higher than 81 of the 83 other technical SEO tools we grade, and level with 2.
It stands best on free plan and trial (A, above 62 of 83) and worst on features (C, above 10).
Yellow Lab Tools has no paid plan.
On features, ease of use and platforms it scores 2.7 out of 4, and no tool on the category's chart scores higher without costing more.
Each grade against the category
Every bar is all 84 technical SEO tools we grade, cut by the letter each got. Yellow Lab Tools’s own letter is outlined.
- AValue for moneyAbove 54 of 83
- AFree plan and trialAbove 62 of 83
- CFeaturesAbove 10 of 83
- BEase of useAbove 62 of 83
- BPlatforms and integrationsAbove 27 of 83
Price against what you get
Each dot is one of 73 technical SEO tools. Further left costs less; higher up scores better on features, ease of use and platforms. Yellow Lab Tools is the marked dot.
What paid plans start at, a month (each step along is roughly double) →
Keep it, or make your own?
Whether this is something you could build for yourself with an AI app builder, and what you would give up.
Keep it
Yellow Lab Tools is free, so making your own would save you nothing.
And it is not the kind of software a weekend replaces. It is one of the better ones too: its GPA of 3.2 is higher than 81 of the 83 other technical SEO tools we grade.
What you could not
- Speed tests run from real browsers on a schedule.
- A real app for macOS and Linux. Something home-made would be a web page.
- An API that other software can build on.
What this rests on. Yellow Lab Tools’s listing: what it does, where it runs, what it plugs into and what it costs. It is a judgement about the kind of software this is. We have not built a replacement for it, and making your own means looking after it too. How we decide, and every tool’s verdict.
Part 05 · Alternatives
The alternatives
The tools it is most often weighed against, side by side
WebPageTest, GTmetrix, PageSpeed Insights, sitespeed.io and Lighthouse
The 5 tools Yellow Lab Tools is most often weighed against, with where each one differs from it.
- 2.6GPA
WebPageTest
Free plan · from $180/yr
Page speed tests from real browsers in locations around the world.
- Only Yellow Lab Tools lists macOS and Linux apps.
- Yellow Lab Tools is open source and self-hostable, according to its own site.
- WebPageTest also covers dashboards.
- 2.8GPA
GTmetrix
Free plan · from $4.99/mo
Page speed testing with Lighthouse reports, monitoring and an API.
- Only Yellow Lab Tools lists macOS and Linux apps.
- Yellow Lab Tools is open source and self-hostable, according to its own site.
- 3.2GPA
PageSpeed Insights
Free
Free Google speed test with real-user Core Web Vitals and Lighthouse.
- Only Yellow Lab Tools lists macOS and Linux apps.
- Yellow Lab Tools is open source and self-hostable, according to its own site.
- 2.6GPA
sitespeed.io
Free
Free open-source toolkit for testing and monitoring web performance.
- Only Yellow Lab Tools lists a web app.
- Only sitespeed.io lists a Windows app.
- 3.2GPA
Lighthouse
Free
Google's open-source audit of page speed, accessibility and SEO.
- Only Yellow Lab Tools lists macOS and Linux apps.
- Only Lighthouse lists a browser extension.
- Yellow Lab Tools is self-hostable, according to its own site.
Part 06 · Questions
Quick answers
The questions people ask about it, each answered in a line or two
12
Questions, each answered in a line or two
The short version of everything above, for when you only need the answer. Each one is told in full in its part of the guide.
Is Yellow Lab Tools free?
Yes. Yellow Lab Tools is free to use.
How much does Yellow Lab Tools cost?
Yellow Lab Tools lists one plan. Free: $0.
What platforms does Yellow Lab Tools work on?
Yellow Lab Tools is available on Web, macOS and Linux.
Does Yellow Lab Tools have an Android app?
No Android app was listed when its pages were read on Oct 23, 2026. Yellow Lab Tools is listed for Web, macOS and Linux.
Does Yellow Lab Tools have an iPhone app?
No iPhone app was listed when its pages were read on Oct 23, 2026. Yellow Lab Tools is listed for Web, macOS and Linux.
Is Yellow Lab Tools open source?
Yes. Yellow Lab Tools is open source, according to its own site.
Does Yellow Lab Tools have an API?
Yes. Yellow Lab Tools offers a public API, according to its own site.
Who makes Yellow Lab Tools?
Yellow Lab Tools is made by Gaël Métais.
What are the alternatives to Yellow Lab Tools?
The closest alternatives to Yellow Lab Tools in our directory are WebPageTest, GTmetrix, PageSpeed Insights, sitespeed.io and Lighthouse.
How does Yellow Lab Tools compare with other technical SEO tools?
Yellow Lab Tools's GPA of 3.2 is higher than 81 of the 83 other technical SEO tools we grade, and level with 2.
Is Yellow Lab Tools good value for money?
ToolGPA grades Yellow Lab Tools A for value for money. Yellow Lab Tools has no paid plan.
Could I make my own version of Yellow Lab Tools?
Yellow Lab Tools is free, so making your own would save you nothing. And it is not the kind of software a weekend replaces.
Where this guide comes from
The prices, plans, platforms and features were read from Yellow Lab Tools’s own pages on Oct 23, 2026, and the grades were given on Oct 23, 2026. Graded from this listing, whose facts were read from Yellow Lab Tools' own pages on 23 October 2026. Not based on using the product, and shorter than our full reviews.
Every tool we list gets five grades, A to F, each with its reason, and a GPA that averages them. How each is decided is at toolgpa.com/grades. This guide is ToolGPA’s own work; it is not made, paid for or approved by Gaël Métais. Prices change, so check yellowlab.tools before you buy.
- yellowlab.tools/about
- yellowlab.tools/
- github.com/YellowLabTools/YellowLabTools
- github.com/YellowLabTools/YellowLabTools/wiki/Public-API
- github.com/YellowLabTools/YellowLabTools/wiki/Command-Line-Interface
- github.com/YellowLabTools/YellowLabTools/wiki/Install-your-private-server
- github.com/YellowLabTools/YellowLabTools/blob/master/lib/metadata/scoreProfileGeneric.json
Part 07 · About
About ToolGPA
Who made this guide, what else is on the site, and how to cite it
3,189
Tools graded, in 94 categories
ToolGPA grades software the way a school report grades a pupil: five subjects, a letter for each with the reason written beside it, and a GPA that averages them. Prices, plans and platforms are read from each maker’s own pages and dated, so you always know how fresh a figure is.
Every grade, review and ranking on ToolGPA is our own judgement. No company can pay for a grade or change one. Every tool on the site has a guide like this one, free to download and pass on. It all lives at toolgpa.com.
3,189
tools graded
94
categories
426
price changes on record
579
apps priced in 12 countries
What else is on toolgpa.com
- Yellow Lab Tools, kept up to dateEverything in this guide, with prices and grades as they are todaytoolgpa.com/tools/yellow-lab-tools
- How grades are givenThe rules behind every letter and every GPAtoolgpa.com/grades
- Value chartsWhat each tool costs against what it scores, for every categorytoolgpa.com/charts
- CompareAny two tools side by side, plan by plantoolgpa.com/compare
- Price changesEvery price rise and cut on record, each with its sourcetoolgpa.com/price-changes
- Prices by countryWhat apps cost on the App Store in 12 countriestoolgpa.com/prices-by-country
- Pay lessEvery public discount: yearly billing, students, nonprofitstoolgpa.com/save
- Keep or makeWhich tools are worth paying for, and which you could build yourselftoolgpa.com/keep-or-make
Scan for the live page
Prices and grades as they are today
Quoting this guide?
Please name ToolGPA and link to the live page, so readers can check the figures for themselves:
ToolGPA, "Yellow Lab Tools: The Insider's Guide", checked Oct 23, 2026. https://toolgpa.com/tools/yellow-lab-tools
Know someone choosing between technical SEO tools?
Send them this guide: toolgpa.com/tools/yellow-lab-tools/guide
ToolGPA elsewhere: youtube.com/@toolgpa
See our other guides
The best-graded technical SEO tools after Yellow Lab Tools, each with an Insider's Guide of its own.
- Technical SEO & Site Audits Insider's GuideEvery one of the 84 technical SEO tools we grade, compared
- Lighthouse Insider's GuideGoogle's open-source audit of page speed, accessibility and SEO3.2 GPA
- PageSpeed Insights Insider's GuideFree Google speed test with real-user Core Web Vitals and Lighthouse3.2 GPA
- Baidu Search Resource Platform Insider's GuideBaidu's webmaster tools for indexing, crawling and keyword data3.0 GPA
Choosing software? Every tool graded, every price dated.
Compare tools at toolgpa.com ›Everything in this guide is ToolGPA’s own summary of what Yellow Lab Tools’s pages, its app-store listings and public reviews said on the dates shown. Grades are our judgement under the rules at toolgpa.com/grades. Every grade, review and ranking on ToolGPA is our own judgement. No company can pay for a grade or change one. Yellow Lab Tools is a trademark of its owner, and this guide is not made, paid for or approved by Gaël Métais. Prices and plans change: check yellowlab.tools before you buy.