Compress PNG to 100KB Online Free

A hundred kilobytes is the number that shows up most often when a form refuses to accept your file. Visa and residence permit applications routinely ask for a photo inside that ceiling, recruitment systems built on Workday or Taleo cap attachments in the same neighbourhood, university admissions portals do it to keep their servers lean, and a surprising number of corporate HR systems still quote figures written back when a megabyte felt enormous. The frustrating part is rarely the compression itself; it is that most general purpose converters either ask you to guess a quality slider or quietly convert the file to JPEG, which kills the transparency or the crisp edges that the form wanted preserved in the first place.

This compressor works backwards from the number instead. You tell it the ceiling, and the encoder searches downward until the file fits, never further than it has to. The first attempt always re-encodes in full truecolor; if that already lands under the limit the file passes through untouched, which means zero measurable quality loss. When truecolor is too heavy, the tool steps through progressively smaller palette sizes, checking each one with a binary search so it settles on the richest palette that still fits rather than the smallest one available. Only those two attempts are made before any dimension changes at all.

Keeping PNG as the output is what protects the details these forms care about. A JPEG output would flood transparent pixels with white and add ringing artefacts around text and hairlines, both of which are reasons an automated photo check can reject a submission. Here transparency survives through the palette route: transparent pixels are assigned a dedicated palette slot and flagged fully clear inside the file’s transparency chunk, so a logo stays cut out and a signature stays free floating instead of landing on a white rectangle.

Typical identification photos sit comfortably within their pixel budget at this target. A passport style crop at a few hundred pixels per side usually reaches the goal during the palette stage without any resampling, which matters because those forms tend to specify pixel dimensions too. Very large scans are the exception: a 3000 pixel institutional scan has enough raw data that the encoder may need to reduce resolution to make the number, and the interface tells you exactly which one happened. If keeping the original dimensions is mandatory, clearing the downscaling checkbox prevents any resizing, and the result row will show plainly whether the target was still met.

Everything is handled by your own browser. The file is decoded onto a canvas, the palette maths and the byte stream are assembled locally, and nothing travels to a server at any point, which is worth knowing when the document carries a photograph, a signature, or identifiers you would rather not have sitting on someone else’s storage. Drop several files in sequence if the form needs multiple attachments, then pull them all down together in one archive and submit with confidence.