A browser add-on for Reddit
See a bot,
say a bot.
SynthStamp puts small community tags next to Reddit accounts, posts, comments and images: bot, AI-written, repost, spam, or vouched human. Tag what you spot, see what others spotted, and make up your own mind.
Useful from your very first tag: whatever you mark stays marked for you, wherever it turns up again.
Free for desktop Firefox. No account needed. Images never leave your browser. What we collect
Caught this sunset on my evening walk
Reminder: please credit the original photographer.
What a stunning capture! The interplay of light and shadow truly showcases the beauty of nature. Thanks for sharing!
How it works
Three things, all inside Reddit.
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1
Spot the flag
A faint flag sits next to the author of every post and comment, and on images. Tagged comments and posts carry their own label. Nothing is hidden unless you switch that on: you see the tags and make up your own mind.
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2
Add your tag
Click the flag and say how sure you are: bot, maybe a bot, maybe human, human. Name the kind of bot if you can tell, or mark an open bot like a subreddit's helper. You can also tag just one comment or image.
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3
It follows them
A tag sticks to the account everywhere it posts. Text and images are recognised when they come back, so a story another account posted before is marked "seen before", with where it was first seen.
The tags
A count of people, never a verdict.
A tag shows how many people tagged something, and as what. SynthStamp itself never decides who is a bot. When people disagree, you see both sides.
On an account
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bot 4
Four people tagged it as a bot, with the kind: AI, repost or spam.
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auto 2
An open bot, like a subreddit's helper. Not a problem, just not a person.
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✓ 3
Three people vouched that a human writes here.
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2 / 3
Contested. Both counts show, and nobody wins.
On a comment, post or image
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AI 3
Tagged as AI-written, or as an AI image.
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repost 5
Seen before, posted as new.
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spam 2
An ad or a link farm dressed up as a comment.
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✓ 1
Someone vouched that a person made it.
Reposts
The picture moves. The tag moves with it.
Your browser turns each image into a short fingerprint, using Meta's open PDQ perceptual hash. The picture itself never leaves your computer. Resized, recompressed and mirrored copies get fingerprints close enough to match, so tags on one copy show on the others.
Heavy crops still slip through for now. Catching them is on the list.
Why people
Detectors guess. Readers notice.
AI detectors get it wrong in both directions, and they can't tell you why. The people reading a thread notice the account that posts every twelve minutes, the photo they saw last week, the comment that says nothing in four sentences. SynthStamp writes that down where the next reader can see it. A little work from each person and a lot for everyone: the same idea that made SponsorBlock work on YouTube.
Fair by design
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4
A flag is a count of people, never SynthStamp's opinion.
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2 / 3
When people disagree, both sides show. Nobody wins by shouting first.
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AI-written 3 · yours
You can change or take back your own tags any time.
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✓
The history of changes is kept, so a bot ring can't tag in bad faith and then quietly wipe its tracks.
What we collect
What we see, and what we don't.
To recognise a repost, the server has to have seen the original. So SynthStamp keeps what its users see on Reddit, not only what they tag. The add-on shows you this again, in full, before it does anything, and one switch in its menu stops it sending what the pages show. Account tags keep showing, and the tags you make are still shared.
Sent to SynthStamp
- The text of posts and comments on the Reddit pages you open, with their authors and links.
- A fingerprint of each image, and the image's web address.
- The tags you make.
- A random id for your install. No account, no email.
- The Reddit username you're logged in as, once a page has shown it. It's used only to keep the counts honest, for example to spot someone vouching for their own posts. It's never shown publicly.
Never sent
- The images themselves.
- Anything from sites other than reddit.com. The add-on doesn't run anywhere else; it only reads the pictures shown on Reddit pages, wherever they are stored, to fingerprint them.
- Your Reddit password, cookies or votes.
- Your email, unless you choose to make an account.
Collection can be switched off in the add-on's menu. Account tags still show.
Where it goes next
Reddit first. Then everywhere people post.
Each new site is added one at a time, listed here and in the add-on before it's switched on. A tag on an image follows it across all of them. Where it's heading: a feed of things people vouched were made by people.
Questions
Is it free?
Yes.
Do I need an account?
No. Install it, read what it collects, turn it on, and reload any Reddit tabs already open. An account keeps your tags when you reinstall or switch browsers, and shows them all in one place.
Can't people just tag everyone as a bot?
They can try. Every tag is a visible count, people can vouch the other way, and a close disagreement shows as contested rather than one side winning. Open the flag and you see both sides' counts. Unusual tagging gets looked at.
What if my account is tagged wrongly?
A tag is what some people said, not a finding. Others can vouch for you. A way to respond to the tags on your own account is planned.
What happens if I delete my account?
Your account, your email and the other personal details on it are removed. The tags stay in the record with no name on them, so nobody can mislead people and then erase the trail. What is kept, and for how long.
Which sites does it work on?
Reddit, both the new design and old.reddit.com. X, Bluesky, Facebook, Instagram, Threads, YouTube, LinkedIn and TikTok are planned, one at a time.
Which browsers?
Firefox on a computer, from Firefox Add-ons. Chrome, Edge and Brave are not in a store yet; a developer build is on the install page. Firefox for Android hasn't been tested. Get the add-on.
That's the third time this exact picture has hit the front page this month.