Free · On-device · Open source

You should never have to pay
to understand something.

Every day you read things you only half-understand — a term, a claim, a paragraph that quietly assumes you know more than you do. The web has one fix for this, and it's a detour: open a tab, paste into a chatbot, lose your place. Or pay $10 a month for a sidebar that does the pasting for you.

Here's the alternative. Highlight anything below.

1Highlight

2Open JustClarify

3Read it in place

a-long-article-you're-reading.com

Why the team hit pause before the release

Late in the sprint, the engineers made an unusual call. Rather than cram in one more feature, they chose to refactor the legacy module first — arguing that the technical debt had grown untenable, and was quietly slowing every new change to a crawl.

Nobody outside the team could see it, but each shortcut taken months earlier was now taxing everything built on top of it.

Click the highlighted phrase to select it — like you would while reading.

This demo is scripted — every answer is pre-written and no AI is called. The real extension generates them live, on your device.

We think the subscription model is backwards. The intelligence already lives on your machine — Chrome now ships an AI model inside the browser itself. Which means explaining what you read can cost nothing, need no account, and never send a word of what you're reading to anyone's server. So that's what we built. Then we open-sourced all of it, so you don't have to take our word for any of this.

Highlight. Read the answer where you stand. Keep going. That's the whole product.

Free, because it costs us nothing.

Tools like this charge subscriptions because every answer costs them server money. JustClarify's answers are generated by your own computer, so our marginal cost is zero — and when the cost is zero, we think the price should be too. No account, no trial, no "you've used your 5 free credits."

Private by architecture, not by promise.

What you highlight never touches our servers, because there are no servers in the loop. The model runs on your machine; airplane mode works. Most privacy policies ask for trust — ours barely has anything to disclose.

Open source, so trust is optional.

The entire extension is public code. Every answer is badged with the exact engine and model that wrote it, and fact-checks only return a verdict with a source you can click. If we ever break these rules, you'll see it in the diff.

For the curious

How a highlight becomes an answer

No magic, no hidden backend. Here is the actual pipeline, straight from the source code:

It reads around your selection, not just your selection. When you highlight, the content script walks outward through the surrounding text and captures a semantic window — about two full sentences on each side for Explain, up to six for Expand. That's why answers fit the article you're in, not a dictionary's idea of the phrase.
The prompt is assembled on the page. Your selection, the surrounding passage, the page title, the action you picked, and your density setting are built into a single prompt locally, inside the tab. At this point, nothing has been sent anywhere.
On-device answers first. The prompt goes to Chrome's built-in Prompt API — Gemini Nano, a model that runs on your own hardware. The first time you use it, Chrome downloads that model once (about 4GB); JustClarify asks before it starts and shows the progress rather than hanging on a silent spinner. After that one download, answers stream into the page with no network round-trip at all. Turn your Wi-Fi off; it still works.
Definitions don't go to a model at all. Highlight a single word and Define queries a real dictionary (the free, keyless Dictionary API) for the actual entry — part of speech, senses, and the dictionary's own example sentence. A definition is a lookup, not a generation; a model can only paraphrase what a dictionary already states, and it can get it wrong. Only words with no entry — jargon, proper nouns, coinages — fall back to a contextual explanation.
Your key, your models — strictly optional. Want frontier-quality answers? Add your own AI Gateway key in settings, and the same prompt routes through one OpenAI-compatible endpoint to whichever model you choose — Claude, GPT, Llama, hundreds of others — and streams straight back. The key lives in your browser's storage and is sent only to the gateway. We never see it, and there is no JustClarify server in between.
The badge never lies. Every answer is stamped with the engine and model that produced it, so an on-device reply and a gateway one can never be confused. Fact-checks return a verdict plus a clickable source — or they don't return at all.

The web ships one version of every page to everyone. JustClarify recompiles it for what you already know.