SmallPDF has built one of the most recognizable brands in PDF tooling. Their web interface is clean, their PDF compression is excellent, and their signing and editing tools work well for everyday PDF tasks. They're specifically designed around PDF workflows and have expanded into a full document platform.
ChangeThisFile is not a PDF platform. It's a format converter — converting files between formats across 9 categories. The overlap with SmallPDF is on PDF conversion routes (DOCX↔PDF, JPG→PDF, PDF→JPG, etc.). Outside that overlap, the tools serve completely different needs.
Quick verdict
For PDF operations (compress, merge, split, sign, edit, fill forms): SmallPDF is the better-designed tool for these workflows.
For format conversion beyond PDF (image, video, audio, ebook, archive, data, font): ChangeThisFile covers formats SmallPDF doesn't touch.
For privacy-sensitive image and data conversions: ChangeThisFile. 193 routes run in the browser — no upload, no server.
For free API access: ChangeThisFile. 25 conversions/month, no daily cap, no card. SmallPDF's API requires a paid plan.
For the most free conversions per day: SmallPDF. Its free tier allows 2 tasks/day; ChangeThisFile's free web tool allows 1 conversion/day, after which it is $2.99 for a 24-hour unlimited day pass or $9.99/month.
For a team document workflow platform: SmallPDF has collaboration, e-signing, and a desktop app that ChangeThisFile doesn't offer.
Pricing comparison
| Plan | ChangeThisFile | SmallPDF |
|---|---|---|
| Free tier (web) | 1 conversion/day — no ads, no signup | 2 tasks/day — twice ChangeThisFile's free allowance |
| Unlock the web tool | $2.99 day pass (24h unlimited) or $9.99/mo Pro | Paid subscription only |
| Free web file size | 25 MB for server-side routes | Capped on free (check their site for the current figure) |
| Free API | 25/mo, no daily cap, no card | No free API tier |
| Entry paid API | $29/mo — 1,500 conversions (all formats) | Individual/team plans (check their site for current pricing) |
| Desktop app | No | Yes |
| E-signing | No | Yes |
SmallPDF's free tier is the more generous one, and this page used to claim the opposite. Two free tasks a day beats one free conversion a day, and there is no way to read that row in ChangeThisFile's favour. Both tools are metered; SmallPDF simply meters at twice the volume.
What differs is the shape of the free tier rather than its size. ChangeThisFile shows no ads, asks for no account, and runs 193 of its routes entirely in your browser, so for those formats the file is never uploaded to anyone. And the unlock is priced for a one-off rather than a habit: $2.99 buys 24 hours of unlimited conversions with no subscription to remember to cancel, where SmallPDF's route past the free tier is a monthly plan. If your question is "how many files can I convert today without paying," SmallPDF is the better answer. If it is "what happens to my file, and what does it cost to finish this one job," ChangeThisFile is.
Feature comparison
| Feature | ChangeThisFile | SmallPDF |
|---|---|---|
| PDF compress | No | Yes — core strength |
| PDF merge / split | No | Yes |
| PDF edit (text, images) | No | Yes |
| E-signing | No | Yes |
| PDF form filling | No | Yes |
| DOCX ↔ PDF conversion | Yes (LibreOffice) | Yes |
| Image → PDF | Yes | Yes |
| PDF → Image | Yes | Yes (limited formats) |
| Video conversion | Yes — FFmpeg | No |
| Audio conversion | Yes — FFmpeg | No |
| Ebook conversion | Yes — Calibre | No |
| Archive conversion | Yes — 7-Zip | No |
| Data format conversion (CSV/JSON/YAML) | Yes | No |
| Font conversion | Yes | No |
| Client-side processing | Yes — 193 routes | No |
| Free daily limit (web) | 1 conversion/day | 2 tasks/day — the more generous free tier |
| Free API tier | Yes — 25/mo, no daily cap | No |
| Desktop app | No | Yes (Windows, Mac) |
Format coverage
SmallPDF is built around PDF. Conversions to and from PDF with Office formats (Word, Excel, PowerPoint) are core. Image to PDF, PDF to image. Their PDF compression and editing tools are the differentiator — SmallPDF can reduce PDF file size, merge multiple PDFs, split pages, add annotations, and handle e-signatures.
ChangeThisFile's roughly 1,000 routes span image (all major formats), document (PDF, DOCX, ODT, RTF, HTML), spreadsheet (XLSX, CSV, TSV, JSON), video (MP4, MKV, WebM, AVI, MOV, GIF, and more), audio (MP3, WAV, FLAC, AAC, OGG, M4A, and more), ebook (EPUB, MOBI, AZW3, FB2, CBR, CBZ), archive (ZIP, RAR, 7Z, TAR, TAR.GZ, and more), data (JSON, CSV, YAML, TSV, XML, TOML), and font (TTF, OTF, WOFF, WOFF2) formats.
SmallPDF doesn't touch video, audio, ebooks, archives, data formats, or fonts. ChangeThisFile doesn't have PDF editing, compression, or signing.
Privacy and data handling
SmallPDF processes files on their servers. They state that files are deleted after a period (check their current policy). For PDFs containing sensitive business information, their privacy documentation is relevant reading.
ChangeThisFile processes 193 routes in the browser — no server, no upload. For image conversions (JPG, PNG, WebP, HEIC, AVIF, GIF, BMP, ICO, SVG, TIFF), data conversions (CSV, JSON, YAML, XML, TOML, TSV), font conversions, and HTML/Markdown conversion, your files stay on your device entirely.
For document PDF conversions (where ChangeThisFile is also server-side), both tools upload over HTTPS. ChangeThisFile auto-deletes files after conversion.
API and developer experience
SmallPDF has a developer API covering their PDF operations — compress, merge, split, convert. The API requires a paid plan.
ChangeThisFile's API covers all format categories including the PDF routes SmallPDF handles, plus video, audio, ebooks, archives, and data formats:
curl -X POST https://changethisfile.com/v1/convert \
-H "Authorization: Bearer ctf_sk_your_key" \
-F "file=@presentation.pptx" \
-F "source=pptx" \
-F "target=pdf" \
--output presentation.pdf
Free tier: 25 conversions/month, no card. Get a key at changethisfile.com/v1/keys/free. If your integration specifically needs PDF compression or PDF merge via API, SmallPDF's API is purpose-built for those operations.
When to choose which
| Use case | Recommended |
|---|---|
| PDF compress, merge, split, edit | SmallPDF |
| E-signing PDFs | SmallPDF |
| Team document workflows (with collaboration) | SmallPDF |
| Desktop app for offline PDF work | SmallPDF |
| Video / audio format conversion | ChangeThisFile |
| Ebook format conversion | ChangeThisFile |
| Archive format conversion | ChangeThisFile |
| Data format conversion (CSV/JSON/YAML) | ChangeThisFile |
| Client-side image conversion (no upload) | ChangeThisFile |
| Free API tier | ChangeThisFile |
| The most free conversions per day | SmallPDF (2 tasks/day vs ChangeThisFile's 1) |
| One day of unlimited conversions without a subscription | ChangeThisFile ($2.99 day pass) |
SmallPDF is excellent if PDF is at the center of your workflow. For a broader file conversion need — especially outside the PDF/Office world — ChangeThisFile covers the ground SmallPDF doesn't: video, audio, ebooks, archives, data formats, and fonts, plus client-side image conversion that keeps files on your device. Both tools serve different primary jobs; many users benefit from having both bookmarked.