Why Exact KB Compression Is Not Always Possible
Learn why quality settings, pixel counts and file overhead produce discrete sizes, and how to handle strict upload limits honestly.
By Nexurivo · Updated
Encoding is not a byte dial
An image encoder turns pixels into a structured file. It chooses representations based on the format, quality settings and image content, but it does not expose a control for every possible final byte count. Changing quality slightly can leave the output unchanged or produce a jump. Whole-pixel dimensions and mandatory file structure add further constraints. A tool can search and measure candidates, but that is different from guaranteeing exactly 50,000 or 200,000 bytes for every image.
Different pictures need different budgets
A smooth background can be represented more compactly than detailed foliage or camera noise. Two images with identical dimensions can therefore have very different sizes at the same quality setting. PNG uses lossless browser encoding, so a JPEG-style quality adjustment does not provide the same size control. Converting formats can help only if the destination accepts the result and the actual encoded output is useful. A format name alone does not predict the savings.
Maximum and Closest solve different problems
Maximum Size looks for an acceptable result at or below the target. Closest Size compares distance to the target and may return a file above it. If an upload rejects anything over 100 KB, a 101 KB candidate is unsuitable even though it is numerically close. Read the destination's wording and use the right mode. A lower bound, if specified, also needs checking separately; a smaller result is not automatically valid for every possible form.
Fixed dimensions can make a target infeasible
General target compression can reduce dimensions after searching quality, but a form may require an exact rectangle. Reducing that rectangle to satisfy bytes would violate another requirement. The fixed-size form and signature workflows therefore report an unmet constraint rather than silently claiming success. A cleaner capture, permitted crop or different accepted format may help. Do not remove required content or repeatedly re-encode a damaged file just to obtain a more convenient number.
Read units and avoid artificial inflation
Nexurivo uses decimal KB and MB: 1000 bytes and 1,000,000 bytes respectively. Other software may use binary units or rounded displays, so a displayed value can be ambiguous near a boundary. Inspect the measured output and leave room below a strict ceiling when needed. Adding meaningless padding would increase bytes without improving detail, and is not a compression solution. If an already small image meets all requirements, keep it rather than inflating it to consume the entire allowance.