Teach students to check a claim before they believe or cite it.
FactSentinel is a free Chrome extension. Highlight a sentence on any web page, right-click, and get a verdict, a confidence level, the reasoning behind it, and source links your class can open and judge for themselves.
Free tier: 10 manual checks and 50 automatic page scans a month. No credit card.
A result students can argue with
A bare true or false teaches nothing. Every FactSentinel check comes back with the parts of the answer that make good classroom material.
Verdict
A clear call on the claim, so a class has something specific to test.
Confidence
How sure the models are. A low score is a good prompt to dig further.
Reasoning
The explanation behind the verdict, written out so students can find the weak step.
Sources to follow
Links to open and read. The habit you want is checking the source, not trusting the summary.
FactSentinel is a first pass, not an answer key. AI models can be wrong. Treat the verdict as a lead and have students confirm it against the sources before they rely on it.
A lesson you can run this week: the viral claim
A short, repeatable activity for a class period, a library session or an advisory block. It works with any claim students already run into.
- Pick a claim. Use a post, headline or screenshot caption your students have actually seen. Ask the class to vote on whether they believe it, and why.
- Check it together. Highlight the sentence, right-click, and run FactSentinel on the projector. Read the verdict, confidence and reasoning aloud.
- Open the sources. Split the class into pairs. Each pair opens one source link and reports back: who published it, what it actually says, and whether it supports the claim.
- Find the disagreement. Manual checks show whether the two AI models agree. When they do not, ask what evidence would settle it.
- Revote and reflect. Did anyone change their mind, and what moved them? Name the habit: check before you share.
Audit an AI citation
Have students run a reference from an AI answer through the checker, then try to locate the real source. Fabricated or mismatched citations make a memorable lesson.
Library research session
Add a "check the claim" step to your database and web research instruction, between finding a source and quoting it.
Compare two checks
Run a claim in a news-style article and in a social post. Compare the evidence behind each and talk about what makes a source trustworthy.
For students: check a source before you cite it
Found a stat, a quote or an AI-written reference for your paper? Run it past FactSentinel first, then read the sources it points to.
- Install it. Add FactSentinel to Chrome and create a free account.
- Highlight and right-click. Select the sentence on any page and choose Fact-Check with FactSentinel.
- Read, then verify. Check the verdict and reasoning, open the source links, and cite the original source, not the checker.
What happens to the text you check
Schools and libraries are right to ask. Here is how it works, in plain terms.
Default mode
The text is sent to AI providers (OpenAI and Anthropic) to produce the verdict. Since September 28, 2026, FactSentinel does not store the text users submit. It keeps only an anonymous fingerprint of the text and the result, and the result is cached for at most 24 hours.
Bring your own keys
If you use your own OpenAI or Anthropic keys, the text goes straight from the browser to that provider and never reaches FactSentinel servers.
Read the full privacy policy before rolling it out with students.
Start free
Most teachers and students will never need more than the free tier. There are no separate school plans.
Free
$0
10 manual checks and 50 automatic page scans per month. No credit card.
$10/month
Platform
100 manual checks and 400 automatic scans per month. Cancel anytime.
$29 once
Your own keys
Unlimited checks using your own OpenAI or Anthropic keys. You pay those providers directly.
See every plan on the pricing page.
Questions from educators
Straight answers, including the limits.
Is FactSentinel free for students and teachers?
You can start free. The free tier includes 10 manual checks and 50 automatic page scans per month, with no credit card. FactSentinel does not have separate school or classroom plans. If you need more than the free tier allows, the Platform plan is $10 per month and the bring-your-own-keys license is a $29 one-time purchase.
Does FactSentinel tell students what is true?
No. It gives a first pass: a verdict, a confidence level, the reasoning behind it, and links to sources. AI models can be wrong, so the point is to give students something specific to open, read and push back on before they believe or cite a claim.
What happens to the text a student checks?
In the default mode the text is sent to AI providers (OpenAI and Anthropic) to produce the verdict. Since September 28, 2026, FactSentinel does not store the text that users submit. It keeps only an anonymous fingerprint of the text and the result, and the result is cached for at most 24 hours. With the bring-your-own-keys option the text goes straight from the browser to the AI provider and never reaches FactSentinel servers. See the privacy policy for the full details.
How do students check something?
Install the Chrome extension, highlight a sentence on any web page, right-click, and choose Fact-Check with FactSentinel. The result shows the verdict, confidence, reasoning and source links. You can also paste a claim into the checker on the website without installing anything.
Which browsers does it work in?
Chrome today. Firefox and Edge versions are listed as coming soon. The website checker works in any browser.
Does it use more than one AI model?
Manual checks in the default mode use two models, one from OpenAI and one from Anthropic, and show whether they agree. Automatic page scans use one model. With bring-your-own-keys, a single key uses one model, and adding both keys uses both.
Can my school or library get help setting this up?
Email [email protected] with your questions and we will reply. There is no classroom dashboard, roster management or LMS integration, so each student or teacher uses their own free account.
More for the classroom
Try it on one claim.
Install the extension and check a single sentence from a page your class is already reading. If it is useful, make it a habit.