How to reduce image file size for uploads (and work within a 20MB limit)

Image file size limits show up everywhere: marketplaces cap uploads per image, email providers limit attachments, website builders slow down with heavy images, and our own tool accepts files up to 20MB. This guide explains what actually determines an image's file size, so you can make files smaller on purpose instead of by trial and error.

The three things that control file size

1. Pixel count

File size grows with the number of pixels. A 4000 × 3000 photo has 12 million pixels; halving both sides to 2000 × 1500 leaves 3 million, a quarter as many. Reducing dimensions is the most powerful way to shrink a file, and for most online uses, you do not need full camera resolution: 2000 pixels on the longest side is enough for marketplace zoom, and 1200 to 1600 pixels is plenty for most websites.

2. Format

The same image can differ in size several times over depending on the format:

• PNG is lossless, so photographic detail compresses poorly. Cutouts saved as PNG are often the largest files.
• JPG is lossy and very efficient for photos, but has no transparency.
• WEBP is lossy (as exported here) and supports transparency, usually producing the smallest files.

Switching a photo cutout from PNG to WEBP often cuts the size by 70% or more. See PNG vs WEBP vs JPG.

3. Quality setting

For JPG and WEBP, the quality setting trades detail for size. The relationship is not linear: going from quality 100 to 90 typically shrinks the file a lot with no visible difference, while going from 70 to 50 saves less and starts to show artifacts. For product photos, 80 to 90 is a good range.

What makes some images larger than others

Two images of the same size and quality can still differ greatly. Fine detail, noise, and texture (grass, fabric, a grainy low-light photo) are expensive to compress. Smooth areas (a plain white background, a clear sky) are cheap. This is one reason product cutouts on pure white compress well as JPG: a large part of the image is perfectly uniform.

Fitting a specific limit

In the bulk background remover, enter a limit in Max file size. For JPG and WEBP exports, the tool lowers the quality step by step for each image until it fits, so every file comes out as large as it can be while staying under the limit. If a file still does not fit at the lowest quality, the tool tells you; choose a smaller size preset for that case.

PNG cannot be shrunk this way because it is lossless. If you need transparency under a size limit, export WEBP instead, or reduce the dimensions.

Some limits you may meet:

Preparing very large photos for the tool

The tool accepts JPG, PNG, and WEBP files up to 20MB. Modern phones and cameras can produce larger files, especially in high-resolution modes (48 to 200 megapixels) or when exporting from RAW. Large photos also need a lot of memory to process: the AI model, the full-resolution image, and the mask all have to fit in your browser's memory, and phones and low-memory computers can run out. That is why, on phones, tablets, and devices with 4GB of memory or less, the tool automatically scales photos larger than about 4 megapixels down before processing.

If a photo is too large or processing fails:

1. Export a smaller JPG from your photo app. Most phone gallery apps let you share or export at a reduced size; on a computer, any editor can resize. 4000 pixels on the longest side is plenty for almost any use.
2. Convert HEIC to JPG. iPhones save photos as HEIC by default. When you share a photo from Photos to a browser upload, iOS usually converts it to JPG automatically. On a computer, open it in Preview (Mac) or Photos (Windows) and export as JPG.
3. Crop first. If the subject is small in a huge frame, cropping to the subject reduces pixels without losing any detail where it matters.
4. Close other tabs on low-memory devices, so the browser has more memory available.

A workflow for web images

For images on your own website or store:

1. Remove the background and keep a full-resolution PNG master.
2. Export a WEBP at about 1600 pixels on the longest side, quality 80.
3. If you need a JPG fallback, export one at the same size, quality 85.
4. Check the result at 100% zoom, especially edges and gradients.

This typically turns a 10 to 20MB master into a web image of 100 to 400KB that looks the same on screen.

Summary

Pixel count, format, and quality decide file size, in that order of impact. Resize to the dimensions you actually need, choose WEBP or JPG over PNG for photos unless you need a lossless master, use quality 80 to 90, and let the Max file size option handle platform caps automatically. For very large camera photos, export a smaller JPG before processing.