How much smaller does WebP make an image? We converted 52 real images to find out

The results in brief

WebP is not a fixed discount. How much an image shrinks depends on how it was stored before: an uncompressed scan has a great deal to lose, a photo saved at high quality has a fair amount, and a small GIF of flat colours has the least. Every result is below, so you can tell in advance what to expect from your own files.

How we tested

We chose 52 images from Wikimedia Commons, every one in the public domain, so anyone can download the same files and repeat the test: 16 photographs taken on eight phones and eight cameras, 14 PNGs (screenshots, charts, logos with transparent backgrounds, maps and three photographic images), 11 GIFs and 11 TIFF scans from US government and Library of Congress collections.

• Each image went through the matching converter with its default settings — quality 85, metadata removed, original size — using the same code and the same limits as a job on this site.
• Public-domain BMP files barely exist, so we saved the 16 photographs and the 10 PNGs without transparency as ordinary 24-bit BMPs and converted those. A BMP stores pixels as they are, so this shows exactly what the format change does.
• To separate the format from the quality setting, we also re-saved each photograph as a JPG at quality 85, with the same encoder settings our JPG converters use.
• Every result was checked: the same width and height, transparency kept where the original had any, and every pixel identical for BMP to PNG. Lossy results were scored with SSIM, a standard measure of how closely one image matches another, where 1.000 is identical.
• We looked at the most-changed area of the lowest-scoring results at 100% zoom, side by side with the original, to judge them for ourselves.
• The first run of this test changed how our WebP converters work: an image with 4,096 colours or fewer is now also tried as lossless WebP, and whichever file is smaller is kept. The results here are from the converters as they now are; the GIF section explains why.
• Sizes are in megabytes of 1,000,000 bytes, or kilobytes of 1,000 bytes below 0.1 MB.

Photographs: JPG to WebP

The typical photo went from 4.7 MB to 1.3 MB, a median saving of 67%. The Nikon photograph of a downy woodpecker went from 7.20 MB to 0.48 MB.

Phones and cameras save their JPGs at a high quality setting, and JPG to WebP writes at 85, so part of every saving comes from that alone. Re-saved as JPGs at 85, the same photos were a median 62% smaller than the originals. The WebPs were a median 31% smaller again than those JPGs, ranging from 17% bigger to 66% smaller. That is WebP's own advantage. They also scored slightly lower for faithfulness (a median SSIM of 0.970, against 0.977 for the JPGs), so like for like the gap is a little narrower than the sizes suggest.

One photo got bigger. A 17-megapixel picture that had already been compressed to 1.04 MB became 1.64 MB, and even a JPG at quality 85 grew by 34%. Saving a heavily compressed image at a higher quality adds bytes without bringing back any detail. If a photo is already small for its size, leave it as it is.

At 100% zoom, in the areas that changed most, WebP had smoothed fine texture: the barring on a hawk's feathers and the noise in an out-of-focus background were a little softer. Faces, edges and outlines looked the same as the original.

BMP to PNG and WebP: the biggest savings, and one lossless

A BMP stores every pixel uncompressed, so either conversion makes it much smaller. The 16 photographs saved as BMP shrank by 33–73% as PNG (a median 62%) and by 90–99% as WebP (a median 97%). Screenshots, charts and maps shrank further as PNG, by 87–98%, because large areas of one colour compress very well; the three photographic pictures among the PNGs shrank by 34–76%.

BMP to PNG is lossless: all 26 PNGs held exactly the same pixels as the bitmaps they came from. BMP to WebP is not, and goes much further on size. For a screenshot or a chart the difference was hard to measure (SSIM 0.994 or higher); for a photograph it is the same trade as JPG to WebP above.

PNG to WebP: smaller, with transparency kept

The 14 PNGs shrank by a median 68%, from 44% for a detailed geological map to 92% for a logo. All four that had transparent areas kept them.

PNG to WebP writes lossy WebP at the quality you choose, and for an image with few colours it also tries lossless WebP and keeps whichever is smaller. Four of the 14 came out lossless, pixel for pixel the same as the PNG: a screenshot, two charts and the geological map. The rest scored 0.990 or higher, except two of the photographic images, at 0.914 and 0.954: their sensor noise and film grain were smoothed, the same effect as on the JPG photographs.

If an image must stay pixel-perfect — a screenshot for a bug report, a chart going into a document that will be edited again — keep the PNG.

GIF to WebP: smaller, and usually exact

The first time we ran this test, five of the nine still GIFs came out bigger, by 16% to 188%. GIF stores a picture made of a few flat colours very compactly, and lossy WebP, designed for photographs, spends more bytes on hard edges and fine patterns; on a street map it also smoothed the dotted shading into flat colour.

So we changed the converter. For an image with 4,096 colours or fewer it now also tries lossless WebP, which stores every pixel exactly, and keeps whichever file is smaller. Run again, all nine still GIFs came out smaller, by 13% to 76% (a median of 30%), and eight of them pixel for pixel identical to the GIF. The street map went from 0.05 MB to 0.03 MB with its shading intact. The ninth, a drawing with soft shading, was smaller as lossy WebP and kept that way. The check costs little: a colour photograph has far more colours than the limit, so it is never encoded twice.

Animated GIFs are not a fair comparison. GIF to WebP keeps the first frame only, so a 228-frame animation of 0.68 MB became a still image of 0.02 MB. To keep the movement, convert the GIF to a video instead.

TIFF scans to WebP

The ten uncompressed scans shrank by 75–99.7%, a median of 94%. The 105.71 MB travel photograph became 5.92 MB, and the 82.32 MB parade photograph 1.90 MB. A Rembrandt etching saved least of these, 75%, because its fine engraved lines are detail WebP has to keep.

One TIFF was already compressed: a topographic map stored with JPEG compression and eight pages. It shrank by 43%, and only its first page was converted, because a WebP holds a single image.

At 100% zoom, the film grain in the plain areas of a scanned portrait was smoothed. If a scan is an archive copy, keep the TIFF and convert a copy for the web.

WebP back to JPG: always bigger

We converted the 16 WebP photos back with WebP to JPG. Every JPG was bigger than the WebP it came from, by between 0.4% and 75%, a median of 31%. That is the price of a format every app can open, and each conversion between lossy formats loses a little more detail (SSIM 0.927–0.994 against the WebP).

Full results

Photographs, as JPG to WebP, the JPG-at-85 control, and the WebP converted back to JPG. Changes are against the original JPG, except the last column, which is against the WebP.

The same pictures saved as BMP, then converted. Every PNG was pixel-identical to its BMP.

PNG, GIF and TIFF to WebP, with each result's SSIM score against the original.

Every image came from Wikimedia Commons and is in the public domain. Fifteen of the photographs were published by the US National Park Service and the US Fish and Wildlife Service, and one by a photographer who released it into the public domain; all are as they were posted, not straight from the camera. The scans come from the Library of Congress, the National Archives, NASA and the US Geological Survey. We tested the copies available on 21 October 2026.

What this means for your images

• Photos for a website: convert to WebP. Expect roughly a third off what a JPG at the same quality would weigh, and more if the original was saved at high quality.
• A photo that is already small for its size may grow. Compare the sizes before replacing the original.
• BMP and uncompressed TIFF: convert. PNG if it must stay exact, WebP if it only needs to look right.
• Screenshots, charts and logos: WebP shrinks them a lot and keeps transparency, but keep the PNG if the image must stay pixel-perfect.
• Still GIFs, charts and simple drawings: convert. With few colours they usually come out smaller and exact.
• Keep your originals. Every lossy conversion loses a little detail, and it cannot be put back.

Choosing between formats in the first place? Read JPG vs PNG and the best image format for websites.