See your thumbnail the way viewers will
A blank canvas lies. ThumbLens drops your thumbnail into a realistic feed — surrounded by other videos, at real size, on real layouts — so you know whether it earns the click before you upload.
Free, with no account and no limits. One permission, no access to your browsing.
Four places people actually see you
Home feed
Your thumbnail in a grid of competing videos, at the size viewers really see it. Light and dark.
Search results
The wide layout, with your title truncating exactly where it will truncate for real.
Suggested sidebar
The compact column beside a playing video — small, cropped, unforgiving.
Mobile
Where most impressions happen, in a phone-sized frame instead of a desktop guess.
Made for the decision, not the design
ThumbLens is not another editor. It answers one question: does this thumbnail win the click in the place it will actually appear?
- A/B compare — up to four versions side by side, same feed, same slot, only the image changes.
- Squint test — blur everything progressively. If it still reads, it works at a glance.
- Title truncation — see where your title gets cut before the cut surprises you.
- Export a PNG — send a client or a collaborator the mockup, not a description.
- Saved previews — your last 50 attempts kept locally, so you can compare with last week's.
Your thumbnails never leave your browser
There is no account, no upload, no server. Images and titles stay in your own browser storage, and
the extension asks for a single permission (storage) — it cannot read the pages you visit.
While you use it, it makes no network requests at all.
Free, and it stays free
Every feature is free: all four layouts, A/B compare, the squint test, PNG export and saved previews. No account, no limits, no ads, no upsell.
If a paid version is ever added it will be for new features — nothing that is free today will be taken away.
The one thing that helps: if ThumbLens saves you time, leave a review. For a free tool with no marketing budget that is what decides whether anyone else finds it.
Install
ThumbLens is a Chrome extension. Install it from the Chrome Web Store, click the toolbar icon, and choose a thumbnail — that is the whole setup.
Independent tool. Not affiliated with, endorsed by, or produced by YouTube or Google.