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All processing for this tool happens in your browser. Your input is not sent to a server.
About this tool
Compress images with manual quality or measured target-KB search across format, quality and dimension settings.
Common uses
- Find a measured output within a file-size requirement.
- Review the quality and dimensions of the actual file before download.
How to use it
- 1.Choose a local image or load the local 256×192 example.
- 2.Choose manual quality or target KB, format and transparency. In target mode enter a size and run the search.
- 3.Review the measured bytes, dimensions, quality and preview; download that same output. An unmet target is reported explicitly.
Executed local examples
100 KB PNG
Local authored 256×192 noisy RGBA example; target PNG 100 KB.
A measured PNG within 102400 bytes is selected from the dimension grid; its exact size depends on the browser encoder.
1 KB PNG
The same local RGBA example; target PNG 1 KB.
No tested PNG dimensions down to 25% fit 1024 bytes in the executed native example. The smallest measured PNG remains available with an unmet-target message.
Limits and notes
- Target search first caps the longest edge at 2000px, then measures dimensions at 100%, 80%, 60%, 40% and 25%. JPEG/WebP test quality 100–10% in steps of 10 at each dimension; PNG only tests dimensions. At most 50 encodes, 30 seconds; each output 20 MiB, cumulative encoding 256 MiB. Prefer the largest tested dimensions and highest tested quality that fit. Exact size or a global optimum over every setting is not promised. Original unchanged; input 20 MiB, 8000px, 40 million pixels. Native decoder/encoder memory cannot be fully bounded.
- The target is an upper bound measured in actual output bytes, not an exact-size guarantee. 1 KB = 1024 bytes. If no tested setting fits, the smallest measured candidate remains available with an explicit unmet result.
- PNG ignores quality. JPEG always fills transparency with white; other formats fill white when transparency is disabled. Manual mode preserves original dimensions. Animated inputs produce the static frame decoded by the browser.
- Target search rejects unsupported native output-format fallback, failed encoding, deadlines and byte limits. The chosen output must decode to its measured dimensions before preview/download.
- File, language, mode or target changes, clear, cancel and leaving invalidate prior results. This tool processes local input without upload or persistence; encoders can differ between browsers.
Frequently asked questions
Does it produce exactly the requested KB?
No. It chooses a measured candidate at or below the limit if one fits. Otherwise it reports that the supported search could not reach the target and keeps the smallest measured result.
How are quality and dimensions selected?
Test the finite dimension grid in descending order and each supported quality. Prefer the largest tested dimensions, then the highest tested quality that fits, without assuming encoded sizes are monotonic.
Can PNG use a quality slider?
PNG is lossless and the quality parameter does not change its encoding. Target PNG search changes dimensions; use manual PNG to retain the original dimensions.