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. 161 routes run in the browser — no upload, no server.
For free API access: ChangeThisFile. 1,000 conversions/month, no card. SmallPDF's API requires a paid plan.
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) | Unlimited, no ads, no signup | 2 tasks/day on free tier |
| Free API | 1,000/mo, no card | No free API tier |
| Entry paid | $29/mo — 10,000 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 notably limited — 2 tasks per day. Their value proposition is in the paid tier, where you get unlimited conversions, compression, editing, and signing. ChangeThisFile's browser tool has no daily limit.
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 — 161 routes | No |
| Free API tier | Yes — 1,000/mo | 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 690 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 161 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: 1,000 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 |
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.