Free · Browser-based · Private

YouTube thumbnail resizer. HD, Full HD, 4K.

Drop any image, pick a quality, and get a perfectly sized thumbnail. The HD preset auto-compresses under YouTube's 2 MB upload cap. Full HD and 4K give you higher-detail exports for blog use, channel banners, and archival.

Runs entirely in your browser using HTML5 Canvas. Your image never leaves your device. How we know.

JPG quality92%

Drop an image, click to choose, or paste from clipboard

JPG, PNG, GIF, WebP, BMP · up to 80 MB · output: HD (1280×720)

Three presets, one tool

Pick the resolution your workflow needs.

YouTube's upload spec is 1280×720, but a thumbnail rarely lives in just one place. Embed players, blog hero images, channel banner crops, social previews — every destination wants something a little different. Three presets cover all of them.

For YouTube

HD

720P

1280×720

YouTube's recommended thumbnail size. Auto-fits under the 2 MB upload cap.

≤ 2 MB · auto-compressed for upload

Full HD

1080P

1920×1080

Higher detail for blog use, channel banner crops, or social previews.

No file-size cap · use as a master export

4K Ultra HD

2160P

3840×2160

Future-proof archival quality. Best for source files you re-export from later.

No file-size cap · use as a master export
YouTube spec

The numbers that actually matter on upload.

FieldYouTube requiresThis tool ships
Resolution1280×720 recommended (640×360 minimum)1280×720 exact (HD preset)
Aspect ratio16:916:9 (auto-cropped from any source)
File sizeUnder 2 MBAuto-fits under 2 MB on HD preset
FormatJPG, PNG, GIF, BMPJPG (default) or PNG
Color spacesRGBsRGB (default browser canvas)
Why this tool exists

Most resizers upload your image. This one doesn't.

Search for a thumbnail resizer and you'll find dozens of sites that send your file to a server you don't control, log it, and serve you ads while you wait. Drafts, internal mockups, screenshots — none of that should leave your machine. This tool runs entirely on your device.

01

Browser-based

Pure HTML5 Canvas. No backend, no server-side processing. Verifiable in your DevTools Network tab — zero outbound requests with image data.

02

Three quality presets

HD for direct YouTube upload, Full HD for embeds and blogs, 4K for archival masters. One tool, three workflows.

03

Auto-fits under 2 MB

On the HD preset, JPG quality steps down progressively until your file passes YouTube's upload cap. No more "thumbnail too large" errors.

04

Works offline

Once the page is loaded, no internet needed. Drop, switch, download, repeat — the whole loop runs locally.

Next step

Sized correctly is step one.
Sized to win the click is step two.

A 1280×720 thumbnail still has to earn the click. Score yours against the top videos in your niche on contrast, face presence, text density, and curiosity-gap signals.

Score it with Thumbnail IQ →
Frequently asked

Questions answered.

YouTube's official upload spec is 1280×720, but creators often need higher-resolution exports for other use cases. Full HD (1920×1080) is what most embed players and blog features want. 4K (3840×2160) is for archival masters you'll re-export from in a year when YouTube inevitably bumps the spec or you need a bigger crop. The HD preset is what you upload to YouTube. The other two cover everything else.
YouTube silently rejects thumbnail uploads larger than 2 MB. Many tools quietly skip this check and you find out only when the upload fails. On the HD preset, this tool starts JPG quality at 92% and steps it down automatically until the file fits under 2 MB. You can override the auto-quality with the slider if you want to try a different point on the size/quality curve. Full HD and 4K presets don't enforce the cap because they're not for direct YouTube upload.
Yes — verifiably. The entire resize runs in your browser via HTML5 Canvas. The image never touches our server, never gets logged, never gets stored anywhere. Open the Network tab in your browser's DevTools while you use the tool: you'll see zero outbound requests with image data. Drop in a private screenshot, a draft thumbnail, an internal mockup, anything. It stays on your device.
The tool center-crops to 16:9 before scaling. So a 1080×1080 Instagram square keeps its center subject and trims the sides. A 9:16 phone screenshot keeps the middle horizontal slice. If you need pixel-precise placement (like a face exactly in the right third of the frame), design your source at the target resolution in Canva, Figma, or Photoshop before uploading.
JPG for photographic content (real-world imagery, faces, product shots, gradients). 5–10× smaller than PNG and the quality loss is invisible at thumbnail sizes. PNG for graphic-heavy content (text overlays, illustrations, hard edges, transparency, screenshots of UIs). Lossless but bigger. The default is JPG because 95% of YouTube thumbnails benefit from it. The toggle is right next to the preset selector — no need to re-upload to switch.
You can, but the output won't actually be sharper than the source. The tool scales the pixels up using high-quality bilinear interpolation, but no algorithm can invent detail that wasn't there. If you upload a 640×360 thumbnail and pick the 4K preset, you'll get a 3840×2160 file that looks like a stretched 360p image. For genuinely higher detail, use a higher-resolution source.
The resize itself is a technical fix, not a CTR boost. What ranks thumbnails is composition, contrast, and the curiosity gap they create with the title. Once you have a properly sized thumbnail, the next move is scoring it against the top videos in your niche. Thumbnail IQ runs face detection, contrast analysis, and a vision-model curiosity-gap read so you know whether your design is competitive before you publish.
Once the page is loaded, yes. Drop an image, switch presets, change quality, download — no network request happens after the initial page load. You can disconnect from the internet entirely and the tool keeps working.