YouTube Thumbnail Size Limit: Get Under 2 MB on a Mac

The limit is 50 MB for video, Shorts and podcast thumbnails uploaded on desktop, and 2 MB for video thumbnails uploaded on mobile. The same YouTube Help page lists the other rules:

Two details trip people up. The 2 MB figure is the mobile cap, so a file that uploads in YouTube Studio on a computer can still fail from the phone app. And Shorts thumbnails can only be added in Studio on a computer, so the phone cap does not apply there.

Use 3840 × 2160 for the recommended size or 1920 × 1080 for a smaller file, both 16:9. YouTube sets a floor of 640 pixels wide, which is a 640 × 360 frame, but a thumbnail shown large on a TV benefits from more pixels.

Pixels are the main driver of file size. A 3840 × 2160 frame has four times the pixels of 1920 × 1080, so it is the first thing to reduce when you are over a cap. We suggest 1920 as a working size for the 2 MB mobile case; that is a judgment, not a YouTube rule. YouTube also asks for a 16:9 ratio, so scale with the fit mode and keep the shape; the fill mode crops. Making clips for other platforms too? See TikTok, Reels and Shorts.

Resize first, then set JPG quality, then read the output size. Smol sets quality and pixel size, not output bytes, so it cannot promise a file lands under 2 MB. You check the result against the cap and run again lower if it misses.

Quality 80 to 85 is where we would start for a face with sharp text on top. Those are starting points, not measured thresholds, so look at the small text and the face edges on a phone-size preview before you upload. JPEG quality also changes color sampling: Smol uses 4:2:0 up to quality 75, 4:2:2 at 80 to 85, and 4:4:4 from 90, and bright red text on a flat color is where chroma shows first.

What does the target file size mode do for thumbnails?

Target-file-size mode (Neural) takes a size between 4 and 4096 KB, so you can type 1800 for a 2 MB cap. It aims at a band, not a hard ceiling, so a file can still land over, and it is slow: about 28 seconds for one small 768 × 512 image. We make no quality claim for it. Use it for the one file that stays over the cap, not for a whole folder.

Compress the folder once and keep the output beside the originals. The same settings cover a test-and-compare set of three variants for one video.

1. 1

   Export the thumbnail from your editor at full size

   Export at 3840 × 2160 or 1920 × 1080 as PNG or JPG, 16:9. Keep the layered file.

2. 2

   Drag the files or the folder into Smol

   A whole folder of variants goes in together. Originals are untouched by default; output is a copy with a _compressed suffix.

3. 3

   Set Compress, output JPG, quality 80, maximum dimension 1920

   For desktop-only uploads at 4K, use quality 85 and 3840. Leave the mode on fit so nothing is cropped.

4. 4

   Run it and read the size of each output

   Smol shows per-file sizes. Find the largest. If it is under 2 MB, every thumbnail clears the mobile cap.

5. 5

   Look at one output at phone size

   Check text edges and faces. If banding or soft text shows, raise quality by 5 and run that file again.

6. 6

   Upload in YouTube Studio or the app

   Remember the account must be phone-verified for custom thumbnails, and for Shorts use Studio on a computer.

The usual cause is a 3840 × 2160 PNG. PNG keeps every pixel exactly, so a thumbnail full of gradients, photo cutouts and glow effects can be many megabytes, while the same frame as a JPG is much smaller. Compress it with output JPG.

• Too many pixels: halve the width to 1920 and the pixel count drops to a quarter.
• PNG for a photographic image: switch to JPG using Compress. Converting a PNG to JPG with Convert ignores the quality setting and writes a large JPEG, so use Compress.
• Grain and noise: high-ISO face shots and added film grain resist compression, so lower quality by 5 and compare.
• Wrong aspect ratio: a non-16:9 file is not larger, but YouTube asks for 16:9, so scale rather than letterbox.

Smol’s own test shows what recompression can do on small images: 24 PNG film photos (768 × 512) came out 69.2% smaller at default quality 75, with the format unchanged, per the benchmark. Camera-size thumbnails will differ, so read your own output sizes. If you want more background on formats, see every Mac method compared.

One more rule applies to the picture itself, not its size: YouTube’s thumbnails policy does not allow a thumbnail that misleads viewers into thinking they are about to see something that is not in the video.

Free options come first. Export settings in your editor and Preview already shrink most thumbnails; a dedicated tool earns its place when you do this weekly, in batches.

Start with the editor export or Preview. For the video file itself, see YouTube upload compression. If you ship a thumbnail a day, the sips command or a Smol Finder Quick Action saves the clicks. Compare against web tools in Smol vs TinyPNG. If a thumbnail is unreleased, it is worth reading what to check before you share an image.

Smol is a Mac app for resizing and compressing, not a thumbnail maker. Skip it in these cases.

• Your file is already under the cap. Smol keeps the original if compressing would make it larger, but there is nothing to gain.
• You need pixel-identical output. Smol always re-encodes images and has no lossless mode; ImageOptim is the better answer.
• You work on Windows or a phone. Smol runs on macOS only, so use your editor’s export.
• You need design, text or cutouts. Smol does not edit images; do that in Photoshop, Affinity or Canva first.
• You need vector output. Smol has no SVG support.