Can I recover the smaller file if I already saved a larger PNG?

Yes, if you still have the original file or can recreate it with the correct settings. Otherwise, you can try re saving the larger PNG with maximum DEFLATE compression and without interlacing or metadata to reduce it as much as possible.

Does changing the PNG bit depth from 8 to 24 always increase file size?

For images with few colours, yes. A 24 bit truecolour PNG stores three bytes per pixel, while an 8 bit palette PNG stores one index per pixel plus a small colour table. The palette version will be smaller for simple graphics.

Is there any reason to use interlacing in a PNG?

Interlacing allows a low resolution preview to appear quickly while the rest of the image loads. This can be useful for very large images on slow connections, but for typical web use the file size penalty usually outweighs the benefit.

What should I do if my automated workflow keeps producing larger files?

Apply the rule of keeping the smaller file. After each compression step, compare the original and the new file size and keep the smaller one. This prevents accidental size increases from any of the causes described above.

Why Did My PNG Get Bigger After Compressing?

You run a compression tool or re-save a PNG and the file gets bigger. It happens constantly. This counter-intuitive result has several specific causes. The main search phrase for this issue is png bigger after compression. Each cause has a straightforward fix. Know them and you keep your PNG files as small as possible.

Editor Saves as Truecolour Instead of Palette

Many image editors default to saving PNGs as truecolour, 24-bit or 32-bit with alpha, even when the original used a smaller palette. A palette image stores colours in a compact lookup table. Truecolour stores every pixel as three or four bytes. For simple graphics, logos, or screenshots, that is far larger.

Switch to Indexed Colour

Open the image and look for an export or save-for-web option.
Choose PNG 8-bit or indexed colour mode if the image has few colours.
For photographs, truecolour is required. For flat-colour graphics, the palette version will be dramatically smaller.

A common scenario: a png file size increased after saving because the editor converted a small palette PNG into a truecolour PNG without warning. Always verify the colour depth before you save.

Low DEFLATE Compression Level

PNG uses the DEFLATE compression algorithm with levels from 0, no compression, to 9, maximum compression. Some programs save at a low level by default. Speed is prioritised. Saving at level 0 or 1 produces a file several times larger than the same image saved at level 9.

If you see an optimized png larger than the original, check the compression setting your tool used. Command-line utilities and image editors let you set the compression level explicitly.

Set Compression to Maximum

Open the save or export dialog.
Find the compression slider, dropdown, or option labelled compression level, quality, or optimization.
Set it to the highest value available. That is 9.

This change alone can reduce file size by a large margin with no visible quality loss. DEFLATE is lossless.

Interlacing Increases File Size

PNG supports interlacing, the Adam7 scheme, for progressive display in browsers. But png interlacing file size is almost always larger than a non-interlaced version of the same image. Interlacing rearranges pixel data into seven passes. That kills DEFLATE compression efficiency.

If your tool enabled interlacing during a save or recompress, the resulting file will be noticeably bigger. Most web images do not need it. Modern connections load images fast enough. Turn off interlacing in the save options.

When a resaved png bigger than the original lands on your desk, interlacing is one of the first settings to check.

Added Metadata and Colour Profiles

Every extra piece of data embedded in a PNG adds bytes. EXIF data, an embedded ICC colour profile, text comments, software-specific chunks. A single ICC profile can add several hundred kilobytes.

If you re-save a PNG and your editor attaches a colour profile or metadata that was not there before, the file size increases. Use an export option that strips metadata. Or remove the profile in a dedicated tool. For most web use, sRGB is assumed. An embedded profile is unnecessary.

Already Optimized PNGs Gain Nothing

A PNG already optimized through a dedicated compressor has little redundant data left to remove. Running another compression pass will not reduce its size. It may increase slightly. Chunk headers and re-encoding choices add overhead.

If you receive a PNG that was already processed, trying to compress it again is pointless. The safe rule in automated workflows: keep the smaller of the original and the new file. That prevents accidentally replacing a well-compressed PNG with a larger version.

Enlarging Dimensions Increases Pixel Count

A small increase in image dimensions directly increases the number of pixels that must be stored. Double the width and height and you quadruple the pixel count. Re-save a PNG after resizing it larger, and the file will be larger regardless of compression settings.

This seems obvious. It is easy to forget during batch processing. Always check that output dimensions match the original unless you intentionally need a larger image. If the dimensions are the same but the file grew, look at the other causes on this list.