Bunny.net is a CDN platform popular for its low prices and straightforward pricing. Its Optimizer add-on handles automatic image compression and format conversion on delivery — your images shrink and get served as WebP without you changing anything. ChangeThisFile is a different kind of tool: a file conversion API where you upload a file and receive it back in a different format.
These tools rarely compete directly. This comparison is for developers who've encountered both and want to know which fits their workflow — or if they need one, the other, or both.
Quick verdict
For automatic image optimization on a CDN you already use: Bunny.net Optimizer. If you're hosting assets on Bunny.net, the Optimizer is an easy add-on that handles WebP conversion and compression transparently.
For converting files between formats programmatically: ChangeThisFile. Free 1,000 conversions/month, 690 routes including video, audio, and documents.
For non-image file types: ChangeThisFile wins by default. Bunny.net Optimizer is image-only.
For the simplest API experience: ChangeThisFile — one POST with a file and a target format, source auto-detected from filename.
Pricing comparison
Competitor pricing below is as of April 2026 - check the vendor's current pricing page before deciding.
| Plan | ChangeThisFile | Bunny.net Optimizer |
|---|---|---|
| Free tier | 1,000 conversions/month (no card) | $9.50/mo (Optimizer add-on) |
| Entry paid | $29/mo — 10,000 conversions | $9.50/mo + CDN bandwidth costs |
| Mid tier | $99/mo — 50,000 conversions | Scales with CDN usage |
| High volume | $499/$1,999/mo | Volume CDN pricing |
| Pricing model | Per conversion (flat count) | Per GB CDN bandwidth + Optimizer add-on |
| Requires CDN? | No — standalone API | Yes — requires Bunny.net CDN |
Bunny.net Optimizer requires you to be a Bunny.net CDN customer — it's not a standalone conversion API. ChangeThisFile has no CDN dependency; it's a direct upload-and-convert service. If you're not already on Bunny.net, comparing just the Optimizer price understates the total cost.
Feature comparison
| Feature | ChangeThisFile | Bunny.net Optimizer |
|---|---|---|
| Free API tier | Yes — 1,000/mo, no card | No — paid add-on |
| SDK required | No — curl/fetch/requests directly | No (CDN, not an API) |
| Image optimization | Conversion (format change) | Yes — auto-compress + WebP/AVIF delivery |
| Video conversion | Yes (MP4, WebM, MKV, AVI, MOV) | No |
| Document conversion | Yes (PDF, DOCX, XLSX, EPUB) | No |
| CDN delivery | No | Yes — global CDN |
| Real-time resize/crop | No | Yes — URL parameter crops |
| Client-side conversions | Yes — 161 browser-native routes | No |
| Webhooks | Yes (HMAC-signed) | No |
| Async jobs | Yes (files >100MB) | No (CDN on-demand) |
What each tool covers
Bunny.net Optimizer works on images served through the Bunny.net CDN. It auto-converts to WebP or AVIF for supporting browsers, applies compression, and can resize via URL parameters. The key distinction: it only works on files already hosted on Bunny.net storage. It's a delivery optimization layer, not a format conversion tool.
ChangeThisFile accepts file uploads and returns converted files. 690 specific conversion routes across 9 categories: image (JPG, PNG, WebP, HEIC, AVIF, GIF, BMP, SVG, ICO, PSD, TIFF), data (CSV, JSON, YAML, XML), spreadsheet (XLSX, XLS), document (PDF, DOCX, ODT, RTF, HTML, Markdown), font (TTF, OTF, WOFF, WOFF2), video (MP4, WebM, MKV, AVI, MOV, 3GP, FLV), audio (MP3, WAV, FLAC, AAC, M4A, OGG), ebook (EPUB, MOBI, AZW3, FB2), and archive (ZIP, RAR, 7Z, TAR). For any conversion that isn't on Bunny.net, this covers it.
API and developer experience
Bunny.net Optimizer isn't a traditional API — it's a CDN feature. You enable it for your pull/storage zone, and images are automatically optimized on delivery. No API calls, no code changes. If you're already using Bunny.net, it's nearly zero effort to enable.
ChangeThisFile API is an upload-and-receive conversion service. No SDK to install — the endpoint is the SDK:
curl -X POST https://changethisfile.com/v1/convert \
-H "Authorization: Bearer ctf_sk_your_key" \
-F "file=@input.png" \
-F "target=webp" \
--output result.webp
Source format is auto-detected from the filename. Get a free API key at changethisfile.com/v1/keys/free — no card required.
The two tools address different problems in a workflow: Bunny.net Optimizer handles delivery-time optimization transparently; ChangeThisFile handles format conversion explicitly as an API call.
When to choose which
| Use case | Recommended |
|---|---|
| Auto-optimize images on Bunny.net CDN | Bunny.net Optimizer |
| Serve WebP/AVIF transparently without code changes | Bunny.net Optimizer |
| Convert image files locally or via API | ChangeThisFile |
| Convert video, audio, documents, or ebooks | ChangeThisFile |
| Free API tier, no card required | ChangeThisFile |
| Simple API — just curl or fetch directly | ChangeThisFile |
| Privacy-first conversion (no server upload) | ChangeThisFile (client-side routes) |
If you're on Bunny.net and want automatic image optimization without changing your code, the Optimizer is a no-brainer add-on. But if you need to convert files between formats — especially outside the image category, or without a Bunny.net dependency — ChangeThisFile's free API tier is a better fit. 1,000 free conversions/month, no card.