What the results show
6 of 7 documents got at least 10 percent smaller at the default level. The largest drop was Expedition 71 Crew Poster Brochure (NASA): 7.21 MB to 773.4 KB (-89.5 percent).
1 of 7 documents changed by less than 2 percent. Field letter (Internet Archive scan) went from 2.23 MB to 2.22 MB (-0.5 percent).
The pattern matches how the tool works: it re-encodes images, so photographed pages shrink and documents that are mostly text, vector art or images in formats it skips do not. A target changes the result only when the file is still too big after the first pass. To try your own file against a size limit, use Compress PDF or one of the size pages such as Compress PDF to 1 MB.
Results
Sizes are the output file size. A cell marked “over” means the tool returned the smallest file it could make, and it was still above the target.
| Document | Original | No target | 0.0976 MB | 0.195 MB | 0.488 MB | 1 MB | 2 MB |
|---|---|---|---|---|---|---|---|
| Attention Is All You Need (arXiv 1706.03762) 15 pages | 2.11 MB | 1.75 MB | 1.75 MB (over) | 1.75 MB (over) | 1.75 MB (over) | 1.75 MB (over) | 1.75 MB |
| IRS Form 1040 2 pages | 215.1 KB | 192.9 KB | 192.9 KB (over) | 192.9 KB | 192.9 KB | 192.9 KB | 192.9 KB |
| Expedition 71 Crew Poster Brochure (NASA) 2 pages | 7.21 MB | 773.4 KB | 93.5 KB | 165.2 KB | 453.2 KB | 773.4 KB | 773.4 KB |
| Album Or. 27.399, page 1 (Leiden University Libraries) 1 pages | 475.9 KB | 315.7 KB | 51.0 KB | 178.5 KB | 475.7 KB | 475.7 KB | 475.7 KB |
| Album Or. 27.399, pages 1-5 (Leiden University Libraries) 5 pages | 1.41 MB | 1.05 MB | 62.7 KB | 111.0 KB | 343.9 KB | 597.7 KB | 1.41 MB |
| Album Or. 27.399 (Leiden University Libraries) 32 pages | 11.43 MB | 8.21 MB | 304.1 KB (over) | 304.1 KB (over) | 304.1 KB | 0.98 MB | 1.69 MB |
| Field letter (Internet Archive scan) 38 pages | 2.23 MB | 2.22 MB | 2.22 MB (over) | 2.22 MB (over) | 2.22 MB (over) | 2.22 MB (over) | 2.22 MB (over) |
The documents
- Attention Is All You Need (arXiv 1706.03762): Research paper, 15 pages, vector text and a few figures. Licence: CC BY 4.0.
- IRS Form 1040: Tax form, 2 pages, text and form fields. Licence: Public domain, US government.
- Expedition 71 Crew Poster Brochure (NASA): Photo poster, 2 pages, one large JPEG. Licence: Public domain, NASA.
- Album Or. 27.399, page 1 (Leiden University Libraries): Photographed album page, 1 page, JPEG. Licence: CC BY 4.0.
- Album Or. 27.399, pages 1-5 (Leiden University Libraries): Photographed album pages, 5 pages, JPEG. Licence: CC BY 4.0.
- Album Or. 27.399 (Leiden University Libraries): Photographed album, 32 pages, JPEG. Licence: CC BY 4.0.
- Field letter (Internet Archive scan): Archive scan, 38 pages, JPEG 2000 and JBIG2 images. Licence: Public domain.
How it was measured
Measured on 2026-10-09 against the service’s release build, with each document sent once with no target and once for each target. Targets are in megabytes of 1,048,576 bytes, and sizes on this page use the same units (KB is 1,024 bytes). Compress first repacks the file, then, only if the file is still above the target, re-encodes page images as JPEG through 7 levels and stops at the first result that fits:
| Level | JPEG quality | Longest image side |
|---|---|---|
| 1 | 75 | 2000 px |
| 2 | 65 | 1600 px |
| 3 | 55 | 1280 px |
| 4 | 45 | 1024 px |
| 5 | 35 | 800 px |
| 6 | 25 | 600 px |
| 7 | 18 | 450 px |
Only JPEG and 8-bit RGB or gray images are re-encoded; 1-bit scans, CMYK, indexed, masked and transparent images and formats such as JPEG 2000 and JBIG2 are skipped. Results depend on the exact documents, so treat them as examples, not guarantees.
Download the data
CSV and JSON, one row per document and target, with original and result size in bytes, whether the target was reached and the percentage change. The script that produced them, web/scripts/measure-compress.ts, and the list of documents are in the repository.