About

YouTube recommends thumbnails at 1280×720 pixels with a minimum width of 640 pixels. Thumbnails with high contrast text and clear focal points achieve click-through rates up to 2× higher than default auto-generated frames. This generator renders directly on an HTML Canvas at the exact recommended resolution, applying composited gradient overlays, drop shadows, and auto-sized typography. No server processing occurs. The entire pipeline runs in your browser using the Canvas 2D API. Note: exported JPEG quality is fixed at 0.92 to balance file size against visual fidelity. For channels covering volatile assets like Bitcoin, rapid thumbnail production matters. Price moves fast. Your content must keep pace.

Formulas

The canvas uses an object-fit cover algorithm to scale any uploaded image to fill 1280×720 without distortion. The scale factor is computed as:

s = max(W_canvasW_img, H_canvasH_img)

where W_canvas = 1280, H_canvas = 720, and W_img, H_img are the source image dimensions. The image is then centered by offsetting:

x_offset = W_canvas − W_img ⋅ s2

Text auto-sizing iterates from a maximum font size downward, measuring via measureText() until the rendered width fits within a safe margin of 90% of canvas width. The gradient overlay uses createLinearGradient with configurable RGBA stops to ensure text legibility against any background.

Reference Data

Platform	Recommended Size	Aspect Ratio	Max File Size	Format
YouTube Thumbnail	1280×720 px	16:9	2 MB	JPG, PNG, GIF, BMP
YouTube Channel Banner	2560×1440 px	16:9	6 MB	JPG, PNG
Twitter Post Image	1200×675 px	16:9	5 MB	JPG, PNG, GIF
Instagram Post	1080×1080 px	1:1	30 MB	JPG, PNG
Instagram Story	1080×1920 px	9:16	30 MB	JPG, PNG, MP4
Facebook Shared Image	1200×630 px	1.91:1	8 MB	JPG, PNG
LinkedIn Post Image	1200×627 px	1.91:1	5 MB	JPG, PNG, GIF
TikTok Cover	1080×1920 px	9:16	-	JPG, PNG
Pinterest Pin	1000×1500 px	2:3	20 MB	JPG, PNG
Twitch Offline Banner	1920×1080 px	16:9	10 MB	JPG, PNG, GIF
Discord Server Icon	512×512 px	1:1	8 MB	JPG, PNG, GIF
Podcast Cover Art	3000×3000 px	1:1	512 KB	JPG, PNG

Frequently Asked Questions

All thumbnails are rendered at exactly 1280×720 pixels, which is YouTube's recommended resolution. The aspect ratio is 16:9. Exported JPEG files typically range from 80 KB to 250 KB depending on image complexity, well under YouTube's 2 MB limit.

The generator uses an object-fit cover algorithm. It scales your image to completely fill the 1280×720 canvas while preserving aspect ratio. If your source image is not 16:9, the excess edges are cropped symmetrically. For best results, use source images that are already close to 16:9 or wider.

Yes, you can upload PNG files with transparency. However, the final export is JPEG, which does not support transparency. Any transparent areas will render as the selected background color (default black). If you need transparency in the output, you can modify the export format in the code to use canvas.toBlob with "image/png".

The algorithm starts at the configured maximum font size and measures the text width using the Canvas 2D measureText() method. If the text exceeds 90% of the canvas width, the font size decrements by 2 pixels and re-measures. This continues until the text fits or a minimum size of 20 pixels is reached. Multi-line text splits on the newline character and each line is sized independently.

The tool includes a one-click fetch from the CoinGecko public API (no API key required). If the API is unreachable due to rate limiting or network issues, the price field remains manually editable. The fetched price is formatted with locale-aware thousand separators.

Nothing leaves your browser. Images are read via the FileReader API as base64 data URLs and rendered onto an HTML Canvas element. No data is transmitted to any server. The generated thumbnail is exported client-side using canvas.toBlob(). When you upload a new image, the previous object URL is revoked to free memory.