Compress PDF

Usually because it is mostly photos or scans and Pictures was left on Keep quality, the default. Lossless compression repacks the file and compacts fonts, but in a photo or scan PDF the pictures are nearly all of the size. Choose Reduce under Pictures to re-encode them; Smallest goes further, with visible loss. If the result says Already optimal, your original was handed back as it was. Usually that is because repacking would not have saved anything; when the reason is different, such as a repack that failed its safety check, the explanation under the result says so. A signed PDF or an XFA form is always returned unchanged, because rewriting it would break the signature or the form.

Reduce scales each picture it can rebuild, screenshots and charts stored as images included, down to about 150 pixels per inch of the page it sits on and re-saves it as a JPEG at quality 82 out of 100, so small text inside a picture can soften. Smallest uses about 110 pixels per inch and quality 60, which shows on close inspection, so keep it for sending rather than archiving. Nothing is ever enlarged, and a picture is replaced only if the new version is smaller. CMYK images, pictures with transparency and a few rarer kinds are left alone, and the notes say how many and why. Every other object in the file is then checked to be unchanged.

Every level preserves content; picture quality is a separate choice under Pictures. Minimal only repacks storage. Balanced additionally checks fonts of at least 32 KiB, up to 2 MB decoded, in documents of up to 20 pages. Maximum checks supported fonts up to 4 MB decoded in documents of up to 80 pages. Font changes require the same full-page preservation checks in both modes, and fonts are never compacted in a PDF with fillable form fields. Some documents produce the same result at different levels.

You can set a maximum size in KB or MB, where 1 MB is 1,000,000 bytes, and the result says Target met or Target not reached with the exact byte count. Filozy never removes content or lowers picture quality to force a size. If a photo or scan PDF misses the limit on Keep quality, try Reduce, then Smallest. If it still does not fit and the recipient accepts several files, Split PDF by size or bookmark can cut it into parts that each fit.

The compressor checks every repacked document object against the original and may compact supported embedded fonts while retaining every glyph ID, shape and spacing. Font compaction requires an all-page pixel and text-position comparison; if verification is unavailable or fails, it falls back to safe repacking. Form fields keep their values and stay fillable, because their objects are checked like everything else. A password-protected PDF is refused rather than silently unlocked: unlock an authorised copy first. Always review the output in your PDF viewer.

Not from a cold start, because the page and its compression code come from filozy.com. Once they have loaded, the work happens in this tab, so you can compress one small file with the settings you plan to use, switch off Wi-Fi, and compress the real one in the same tab. Font compaction fetches a 600 KB engine the first time a file needs it; offline, that step is skipped and the file is still compressed. Processing details under the result shows the requests this page made during the job, but not those made by the background worker that does the compressing, such as the font engine download. Your browser's Network panel lists the worker's requests too, and your PDF is never one of them.