i built a free chrome extension that audits any website for SEO problems in 10 seconds

i already had a python SEO scanner running on my server. it checks 10 different things — title tags, meta descriptions, alt text on images, heading hierarchy, structured data, canonical URLs, viewport tags, page speed, HTTPS, and open graph tags. scores every site out of 100.

problem was nobody could use it without hitting my API. so i rebuilt the core scanning logic as a chrome extension that runs entirely in the browser. no API calls, no server, no account needed. click the icon, get your score.

how it works

the extension injects a content script that scans the current page DOM. it checks:

• does the page have a title tag? is it the right length?
• is there a meta description? too short or too long?
• how many images are missing alt text? (this one is usually ugly — most sites have 30-60% of images with no alt)
• is there a proper heading hierarchy? (h1 before h2 before h3, no skipping)
• is there structured data (schema.org)?
• does it have a canonical URL set?
• is viewport configured for mobile?

it runs in under a second and shows a score out of 100 with a breakdown of what is passing and what is failing.

free vs pro

the free version shows your score and the top 5 issues. the pro version ($9/mo) shows everything — full issue list, suggestions for fixes, and export to CSV.

i built this in about 4 hours. most of the logic was already written for the python version. translating it to vanilla JS for a chrome content script was straightforward.

what i learned building it

1. chrome extensions are underrated as products. they have built-in distribution through the chrome web store. people search for "SEO checker" and find you. no cold emails needed.

2. manifest v3 is annoying but manageable. the main gotcha is that content scripts cant access certain APIs directly — you need message passing between the content script and the popup.

3. a free tier is essential. nobody installs a paid extension from an unknown developer. the free version builds trust, the pro version captures value.

4. the hardest part isnt the code — its getting the first 100 installs. same distribution problem as everything else.

the extension is packaged and ready. currently figuring out the best distribution channel — chrome web store, direct download, or bundled with the server-side tool.

if you want to try the server-side version, its free: https://vemtrac-outreach.pages.dev

anyone else built chrome extensions as a revenue stream? curious what install numbers look like for niche developer tools.