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Inspiration
Misinformation spreads fast, and elderly people are often the most affected. They frequently run into misleading headlines and false claims with no easy way to check if something is true. We wanted to build a simple tool that anyone could use, no technical background needed. That is what led us to TruthLens: a fact-checking extension that works right in your browser.
What it does
TruthLens is a Chrome extension that lets you fact-check claims without leaving the page you are on. You can type or paste a claim into the popup, or highlight text on any webpage and import it with one click. The extension sends it to the Gemini API, which checks up to five factual claims and returns a verdict with a short evidence summary and source links. Everything shows up in the popup with no extra steps.
How we built it
TruthLens is a plain HTML, CSS, and JavaScript Chrome extension with no build step needed. The popup handles the UI, and popup.js takes care of grabbing selected text, sending requests to the Gemini API, and displaying the results. Google Search grounding is enabled on every request so real sources show up alongside each verdict. The API key is stored in a local config.js file that is excluded from version control.
Challenges we ran into
Our biggest issue was the API. We started with the Google Fact Check API but kept running into problems with its reliability and what it could do. We eventually switched to the Gemini API with Google Search grounding, which gave us the accuracy and flexibility we needed. The switch took time but the final result was much better.
Accomplishments that we’re proud of
Getting the extension fully working and returning accurate results was our biggest win. Fact-checking seems simple, but getting the whole pipeline from user input to clean output in the popup to work reliably took a lot of work. Seeing it return a well-sourced result for the first time made all the earlier frustration worth it.
What we learned
TruthLens showed us how important it is to adapt when something is not working. Switching APIs mid-project touches everything from code structure to how you handle responses. We also learned a lot about designing for non-technical users, where keeping things simple has to come first.
What’s next for TruthLens
We want to improve both accuracy and automation. For accuracy, we are looking at pulling from multiple APIs at once, combining Gemini and the Google Fact Check API for better results. For automation, we want to add background page detection that can flag potentially false claims as you browse without any manual input needed.
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