Judge a compressor by its size box, not its presets
Upload forms check bytes, not quality settings, so the compressor that accepts your target size beats the one offering three presets and a prayer. PDFGym takes the number as input and verifies the text survives. The big suites offer presets or manual dials instead, which suits tuning by hand but not landing on a stated limit.
Who needs which kind
A visa applicant faces a field that rejects anything over 200 KB. Her scan exports at 3.1 MB, and the consulate portal closes on Sunday. She needs a size box: type 200 KB, get a file under 200 KB, done. Presets named after quality levels answer a question nobody asked her.
A designer preparing a portfolio has the opposite problem. No portal, no limit, just a 90 MB file that feels rude to email. She wants to eyeball the tradeoff herself: nudge quality down, check the images, stop when it looks right. Manual dials and presets fit her evening better than a byte target. Know which person you are before you pick.
Four compressors compared
iLovePDF's compressor page names three compression levels: Extreme, Recommended and Less compression. Smallpdf's page offers Basic, Moderate (Pro) and Strong (Pro), describes its tools as cloud-based, and states files are automatically deleted after one hour. PDF24's page exposes DPI, image quality, grayscale and strip options with the same one-hour deletion. All checked 2 November 2026. The comparison:
| PDFGym | iLovePDF | Smallpdf | PDF24 | |
|---|---|---|---|---|
| Size input | PDFGym Type the target Presets plus any exact cap. | iLovePDF Three levels Extreme, Recommended, Less. | Smallpdf Three levels Basic free; two need Pro. | PDF24 Manual dials DPI, quality, grayscale, strips. |
| Text protection | PDFGym Read back before download Output checked against the source. | iLovePDF You check by eye | Smallpdf You check by eye | PDF24 You check by eye |
| Free depth | PDFGym Everything free No tier, no account, no ads. | iLovePDF Free with limits See its comparison page. | Smallpdf Basic free only Deeper cuts need Pro. | PDF24 Free, no limits Funded by page ads. |
| File leaves your machine | PDFGym No. Never | iLovePDF Online processing | Smallpdf Cloud, deleted in an hour | PDF24 Cloud, deleted in an hour |
Where the big suites win
Control and company. PDF24's dials, DPI, image quality percentage, grayscale conversion, metadata and attachment stripping, suit anyone tuning quality by hand rather than chasing a number. iLovePDF and Smallpdf wrap compression in full suites, so the squeezed file can be converted, signed or merged without changing sites. For the designer's portfolio evening, that breadth beats a single size box.
Smallpdf's comparison page and iLovePDF's comparison page cover each suite's free limits in detail, and the PDF24 comparison covers the ad-funded model. Read the one matching the tool you already use.
Where PDFGym fits
At the upload form with the stated limit. The compressor takes the target as presets of 100 KB, 200 KB, 500 KB, 1 MB and 2 MB, or any exact cap you type, then runs four techniques at it: a clean structural re-save, image downsampling, font subsetting, and a last-resort raster redraw. Every result is opened again and checked against the original before download.
That check is the point. Heavy compression can flatten text into pictures: small file, dead text, discovered only when someone searches for a name inside it. Whether the exact number lands depends on the file itself. Scanned pages built from images shrink most, while text-only documents are already small and leave little to remove.
How to test compressors yourself
Take one real file, the kind you actually send, and run the same file through each candidate. Then check three things: the resulting size in bytes, whether the text stays selectable, and whether images stay legible at the magnification your reader will open.
That ten-minute test beats every review, including this one. A roundup that never ran a file is only repeating vendor pages; your document and your recipient's limit are the only judges that matter. The merge and compress guide shows the batch version of the same workflow.
How we checked
We read the iLovePDF, Smallpdf and PDF24 compressor pages on each vendor's own site for the levels, dials and deletion claims quoted above, all checked 2 November 2026, and matched the PDFGym side against the compressor tool page in this repository. We created no accounts, uploaded no documents and ran no timed compression tests.
Short answers about PDF compressors
- Which compressor accepts an exact file size?
- The PDFGym compressor takes presets or any exact cap you type and works toward it with four techniques. The suites offer quality levels or manual dials instead, which means guessing and re-running until a result lands under the limit.
- Can compression destroy my text?
- Yes, if the tool flattens pages into images. PDFGym reopens every result and checks it against the source before download; with other tools, select a sentence in the output before sending it.
- Why do compressors disagree on the same file?
- They shrink different things: image resolution, image quality, font data, object cleanup, or the whole page flattened to a picture. The last gives the smallest file and kills the text, which is why outputs need checking.
- How small can a PDF get?
- It depends on the contents. Scanned pages built from images have the most to give, while small text-only files have the least. The number that matters is your recipient's limit, not a headline percentage.
Compressors and size guides
- Compress PDF Type your target size and get a verified file back.
- PDFGym vs iLovePDF Weigh the preset suite against the size box.
- PDFGym vs Smallpdf Weigh the Pro-tiered suite against the free tab.
- PDFGym vs PDF24 Weigh the manual dials against the size box.