Lossless vs Target-Size PDF Compression
By PDFOak · Published September 9, 2026 · Updated October 1, 2026
Lossless compression keeps document features intact but may save little. Target-size compression can go much smaller by recompressing the images.
Neither is stronger in every case. They answer different constraints: “must stay searchable” against “must be under this many bytes”.
Lossless
It repacks objects and removes safe structural waste. Visible content and existing image data stay unchanged, so results range from a useful saving to none at all. It is the default for contracts, accessible documents and court filings.
Target size
It downsamples and recompresses the images inside the file, searching resolution and JPEG quality for the best result under your ceiling, while the text stays selectable and searchable. The cost is image sharpness. If a text-heavy file still cannot fit, the tool says so and names the smallest size it reached instead of rasterizing; scans and image-only documents are rasterized to reach the target, which removes any text layer.
When both requirements are hard
A text-heavy file that must be searchable and under a small limit may be out of reach: the tool will report the smallest size it got to. For a scan, compress first, then run OCR to add a text layer to the smaller file. OCR uploads the file and recognizes English only.
A simple decision rule
- Write down the real size ceiling.
- Decide whether text selection, forms, links or accessibility must survive.
- Try lossless first when structure matters.
- Use target-size mode only if the lossless result is still too large.
- Keep the source and check the final file.
Frequently asked questions
Which mode gives the smaller file?
Target size, usually, because it is allowed to change the page images.