How we tested
A transparency note up front: free-tier limits change constantly, so every limit below is given as publicly stated on each tool's own site, with "check current site" wherever a number is likely to have moved. Size-reduction ranges are illustrative — your files will vary.
Same three test files through every tool:
For each tool we checked: can you compress with no account at all? What is the maximum file size accepted on the free tier? How many free tasks per hour or day before you are cut off? Does the free output carry a watermark? What quality controls exist — presets only, or exact control? And does the file get uploaded to a server or processed locally?
What we found, in broad strokes (illustrative ranges): text reports typically shrink 40–70%, image-heavy decks 20–50%, and scans 30–60% at visually acceptable quality. The spread between tools on the same file was smaller than the marketing suggests — the real differences are limits, watermarks, and control, not magic algorithms.
- A 12-page text report with charts — the "office document" case.
- A 30-slide image-heavy deck — the "hard to shrink" case.
- An 8-page scanned document — the "everything is an image" case.
The comparison table
Two honest caveats: first, "no signup" sometimes means "no signup for your first two files today" — that is why the limits column matters more than the headline. Second, we could not fully verify PrivacyPDF's current free-tier terms at writing time, so treat that row as a starting point, not a verdict.
- all-done — truly no signup: yes; max file size (free, as stated): check current site; free-tier limits: none stated; watermark on free output: no; quality control: quality slider (10–90% compression level) plus result readout after each run; files processed: in your browser
- PDF24 Tools — truly no signup: yes; max file size (free, as stated): generous caps as stated; free-tier limits: none notable; watermark on free output: no; quality control: presets; files processed: uploaded to server
- Sejda — truly no signup: yes; max file size (free, as stated): 200 pages or 50MB (as stated); free-tier limits: 3 tasks/hour (as stated); watermark on free output: no; quality control: quality presets plus options; files processed: uploaded, deleted hourly per their policy
- iLovePDF — truly no signup: yes, within free tier; max file size (free, as stated): caps as stated; free-tier limits: task limits per hour/day — check current site; watermark on free output: no; quality control: compression-level presets; files processed: uploaded to server
- Smallpdf — truly no signup: yes, within free tier; max file size (free, as stated): caps as stated; free-tier limits: around 2 free tasks/day historically — check current site; watermark on free output: no; quality control: limited options on free; files processed: uploaded to server
- compress2go — truly no signup: yes; max file size (free, as stated): caps as stated — check current site; free-tier limits: daily limits — check current site; watermark on free output: no; quality control: presets; files processed: uploaded to server
- PrivacyPDF — truly no signup: claims no signup; max file size (free, as stated): check current site; free-tier limits: check current site; watermark on free output: check current site; quality control: check current site; files processed: check current site
Mini-reviews: each tool's catch
Smallpdf — the most polished interface of the bunch, and compression quality is genuinely good. The catch is the free task wall: historically around two tasks a day, which is fine for a one-off but maddening if you are working through a batch.
iLovePDF — solid compression presets ("less" vs "more" compression) and reliable output. The catch is hourly/daily task throttling on the free tier; check the current numbers on their site before planning a big job around it.
Sejda — the most generous free caps we have seen stated anywhere (200 pages or 50MB), which makes it the pick for occasional huge files. The catch: three tasks per hour, so it is a "one big file at a time" tool, not a batch workhorse.
PDF24 Tools — refreshingly straightforward: no signup, no watermark, no games. The catch is simply that controls are basic presets — fine for "make it smaller," less ideal when you need an exact target size.
all-done — no signup, no watermark, and the standout feature: a quality slider (10–90% compression level) with an instant result readout after each run, so you can iterate toward an exact size (100KB for a portal, under 10MB for email) instead of guessing with presets. Files are processed in your browser rather than uploaded. The catch: it is a focused tool, not a 20-tools-in-one suite.
The privacy question nobody asks
Here is what "free online compressor" usually means mechanically: your file is uploaded to someone's server, processed there, and (they say) deleted after some hours. Most reputable tools state deletion windows in their privacy policies — commonly 1 to 24 hours — but during that window your document sits on infrastructure you do not control.
For most files, that is fine. For contracts, medical records, financial statements, or anything with personal data, it should give you pause. Your options: a desktop app (nothing leaves your machine, but you have to install something), or a tool that processes the PDF locally in your browser — the file never uploads at all. That is how all-done's compressor works: the compression happens on your device, so there is no server copy to worry about.
Which should you pick?
- Sensitive documents — a browser-local tool (all-done) or a desktop app. Nothing uploaded, nothing to delete.
- One huge file, occasionally — Sejda's generous stated caps, within the 3-tasks-per-hour limit.
- An exact target size (100KB portal cap, sub-10MB email) — a quality slider plus result readout (all-done) beats preset guessing.
- Batch jobs — check daily/hourly task limits first; free tiers are designed to throttle exactly this. Splitting work across days, or a desktop tool, saves frustration.
- "Just make this one PDF smaller, right now" — any of the above; pick the one with the fewest clicks between you and the download button.
