SynthStamp is on Firefox Add-ons

SynthStamp passed Mozilla’s review and is live on Firefox Add-ons. You can install it in two clicks, with no account, and start tagging.

That makes this the first day the store version has run against the real thing, on a real person’s Reddit, talking to the real server. Here is how that went.

It works

Within a few minutes of installing, the first tags landed: a repost bot, an AI account, and a handful of people vouched as human. The flags showed up next to their usernames straight away, on the thread where they were tagged and on every other thread those accounts appear in.

In about ten minutes of ordinary browsing, one browser had sent what it saw on roughly sixty posts: a little over a thousand comments from 440 accounts. That is the memory reposts get matched against, and it started from zero this afternoon. Every person who installs adds to it just by reading.

The first bug took under an hour

Then we looked for the image flags, and there weren’t any. Not one picture had been fingerprinted.

The cause was plain once we looked. SynthStamp fingerprints an image by reading its bytes in the browser, and Reddit serves its pictures from a separate address that refuses to let anyone but reddit.com read them. Our test pages serve their images from our own server, so every test passed, and the one thing we couldn’t test, real Reddit, was exactly where it broke.

The fix is version 0.1.1. It asks Firefox for permission to read images from Reddit’s image hosts, which is the honest way to say what it was already trying to do. The images still never leave your browser; only the fingerprint does. Firefox will show the new permission when it updates, once Mozilla has reviewed it.

We also tidied two smaller things the first day showed us. A browser with several Reddit tabs open used to register itself several times over, and now registers once. And the add-on’s menu had a “server” setting left over from development that nobody should ever need; it’s gone.

What a first day teaches

You can test an add-on against saved copies of a site for weeks and still learn something in the first ten minutes on the real one. We wrote about why we test against copies: Reddit, reasonably, turns automated browsers away. The cost is that the first real visitor is the first real test. Today that visitor was us, which is the best case.

What’s next

• 0.1.1 through review, so image tags work everywhere.
• Chrome and Edge. The add-on already runs there; the store listings are next.
• More of Reddit seen. Repost matching gets better with every thread someone reads.

If you use Reddit in Firefox, get the add-on. It’s useful from your first tag: whatever you mark stays marked for you, wherever it turns up again. And if you see a bot, say a bot.