A compression tool creates a candidate file; that candidate is not always smaller. The original may already be efficiently encoded, the chosen format may need more bytes or the output settings may preserve more information.
1. You converted a photo to PNG
PNG does not discard image detail through JPEG-style quantization. Saving a decoded photograph as PNG can therefore require more bytes than its JPG or lossy WebP source. The new file does not regain detail that was lost earlier.
2. The original was already efficient
Browser encoders do not reproduce every optimisation used by desktop tools. In our desktop Chrome test on 26 October 2026, a generated 900 × 900 PNG sample remained at 442.5 KB and was labelled Original kept. That indicates the new candidate was at least as large, so the original bytes were returned. This is expected behaviour, not failed processing.
3. You increased dimensions or changed the canvas
More pixels may require more bytes. Padding also changes what must be encoded. A lossless encoder can compress repeated flat colours well, but there is no universal relationship between canvas area and final file size.
4. You selected a higher quality setting
A high-quality JPG or WebP re-encoding may need more bytes without restoring detail from the source. Each browser’s quality scale can behave differently, and 82% is not a promise to retain exactly 82% of the original information.
What this tool does about it
When format, dimensions and image geometry are unchanged, a candidate at least as large as the original is replaced by the original. Conversion, cropping and other requested edits still need their newly encoded output, even if it is larger. An original kept by this safeguard also keeps its metadata.
Steps to reduce the file
- Keep your original source.
- For JPG/WebP, try a lower maximum quality or choose Target file size.
- Allow smaller dimensions only if the destination permits them.
- For PNG, compare a smaller pixel size or WebP if accepted.
- Inspect the exact target status and visual result before sharing.
ZIP is for convenience
The ZIP download packages image files without another lossy encoding step. Archive headers add a small amount of overhead, so the ZIP itself need not be smaller than the sum of the images.
Choose whether to keep photo metadata
Preserve supported metadata is selected by default. EXIF dates, camera details and GPS are retained when present, while orientation and dimensions are updated for the newly encoded pixels. PNG text and dates, and JPG comments, stay when keeping their format. XMP, IPTC and original colour profiles are not transferred during re-encoding; embedded preview links are cleared. Retained data counts toward target file sizes.
Choose Remove metadata to omit source metadata. This always re-encodes and disables the original-file fallback, so a result may be larger. For metadata removal without recompressing the image pixels, use Metadata Remover. Downloaded file creation and modification dates are separate from an embedded photo date and may change.
Behind the result
Learn why re-encoding or conversion can increase file size, when the original is kept and how to get a smaller result.
What does encoding mean?
Decoding turns the bytes in an image file into pixels that a browser can display. Encoding turns pixels back into a file, using the rules of JPG, PNG or WebP. It is not encryption. Our compression and conversion tools decode locally, draw the image onto a canvas and call the browser’s canvas.toBlob encoder. The browser supplies the codec, so results can vary between browsers.
How JPG compression works
JPEG commonly splits image information into small blocks, uses a discrete cosine transform to describe patterns within them, then rounds transform coefficients in a step called quantization. Coarser rounding saves space but discards detail. The remaining values are efficiently coded into bytes. Our quality control is passed to the browser encoder; it is not a percentage of original detail retained or a guaranteed percentage reduction. Repeated JPG re-encoding can introduce additional artefacts.
How PNG encoding works
PNG uses reversible filters on pixel rows followed by DEFLATE compression. These steps can represent the encoded pixels without JPEG-style quality loss. PNG ignores the quality slider. This tool uses the browser’s PNG encoder, rather than a dedicated palette-reduction optimiser, so an already efficient PNG may not get smaller. Resizing or colour handling before encoding can still change pixels; lossless encoding does not promise that the whole editing pipeline preserves the original file.
How WebP compression works
Lossy WebP predicts image regions from neighbouring pixels, transforms the difference and quantizes it before coding the result. The format also supports a separate lossless mode, but this tool requests browser WebP encoding with a quality setting and does not expose a guaranteed lossless mode. Transparency can be retained. A lower quality setting often reduces size, although sharp text and fine textures may suffer.
Why the original may be kept
After encoding, the tool compares byte sizes. With Preserve supported metadata selected, when format, dimensions and geometry are unchanged and the new file is not smaller, it keeps the original bytes. This avoids a larger replacement. A retained original also retains its metadata: use the Metadata Remover when privacy cleaning is the goal. ZIP download bundles the files without another lossy image-encoding step.
Where processing happens
Your selected image is processed on your device, without an image upload. Canvas exports are new files and may change embedded metadata or colour information. Keep a master copy for archival work. Animated PNG and animated WebP are rejected; these tools handle static images.
How target-size compression works
Choose 100 KB, 200 KB, 500 KB or a custom decimal-KB limit. For JPG/WebP, the tool tries quality values from your selected maximum down to 10% and refines a successful bracket with a bounded binary search. When you explicitly allow smaller dimensions, it can also try up to eight downsizing steps. PNG ignores quality. Exact resizer dimensions are preserved. Only a measured output within the byte limit is marked Target met; otherwise the smallest tested candidate is marked Above target. This is a bounded search, not proof of a globally optimal result.
Metadata choice
Preserve supported metadata is the default: EXIF dates, camera and GPS fields are copied, with orientation reset after decoding and dimensions updated. PNG text/dates and JPG comments stay within their format. XMP, IPTC and original colour profiles are not transferred; embedded preview links are cleared. Retained metadata is included in target-size measurements. Remove metadata omits source metadata and disables the original-file fallback. Filesystem download dates are separate.
Explore the details: Browser encodingImage formats — MDN