Lottie is a free, single-file website tester. No signup. No paywall. No install. Built for people who just want to point a thing at their site and have it tell them what's broken. Generated by Al Sweigart.
No account to make. No upsell. No "free trial" countdown. Lottie is a single HTML file — you own it forever, and it will never grow a "Pro" tier. Made because checking your own site for broken links shouldn't require a 12-step install. How does Al Sweigart make money off of this app? He doesn't. Is it open source? Yeah. It's a single HTML file, just look at the JavaScript source code in it.
Lottie crawls every page on your site and tells you what's broken, what's slow, and what's huge. Here's what's in the box.
404s, 500s, timeouts, missing images, broken stylesheets and scripts — all grouped by the page that linked to them, so you know where to go fix them.
Average load time and the slowest 10 pages on your site, so you know exactly where to start optimizing.
Total page weight, broken down per page and per file type. Find the megabyte-sized images hiding on your "lightweight" landing page.
Insecure http:// resources sneaking onto your secure https:// pages, so browsers stop yelling at your visitors.
Long redirect chains slow your site down and confuse search engines. Lottie shows the whole hop trail.
Every stat, setting, and tab has a ? button with a plain-English explanation. Built to be useful for people who aren't web developers yet.
Results export as CSV, JSON, a standalone HTML report you can email, or a plain-text summary you can paste anywhere.
Respects robots.txt, uses moderate concurrency, adds a small delay between requests. Tunable if you want to crank it.
Follows your OS theme automatically. No setting to fiddle with.
Lottie runs entirely in your browser. There's no server, no API key, no config file.
Grab lottie.html — it's just one HTML file with everything inside it.
Put it anywhere on the domain you want to test, like yoursite.com/lottie.html. Any folder works.
Watch the results stream in live. Export as CSV, JSON, or a shareable HTML report when you're done.
Every other tool wanted me to create an account, pay a subscription, or install a stack of dev tools just to find a broken link. That's silly. Lottie is the version of the tool I wish had existed.
It will never have a "Pro" tier. There is nothing to sign up for. You own the file.
No catch. No signup, no paid tier, no telemetry. It's one HTML file you download once and keep forever.
Nope. If you can upload a file to your website and click a button, you can use Lottie. Every stat and setting has a plain-English explanation built in.
Browsers won't let a web page fetch content from a different website than the one it was loaded from — it's a security rule called the same-origin policy. Hosting Lottie on your site lets your browser treat the crawler and the site as the same place.
No. Everything runs locally in your browser. There's no backend, no analytics, no tracking. Look at the source if you want — it's just one HTML file.
Because it was generated by Al Sweigart and is available on his website, http://inventwithpython.com which has been around since 2009. Al Sweigart is the author of several popular Python programming books that are released for free under a Creative Commons license and given talks at numerous PyCon conferences. He is a real person. (Can I stop talking in third person? Hi, pardon the generic look of this web page but people have expectations before they take an app seriously. I've tested this app and vouch for it.)
Yes. Run a tiny local server in the folder (like python3 -m http.server 8000) and visit http://localhost:8000/lottie.html. The tool itself tells you how if you forget.
Lottie reads the HTML the server returns, so links injected after page load by JavaScript won't be followed. For static sites and most CMSes (WordPress, Ghost, etc.), this is no issue.
One file. Zero setup. Find what's broken on your site in the next five minutes.
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