This page lists what edgesharp does and doesn’t support, side-by-side with
Next.js’s default image optimizer (which on Vercel uses Sharp/libvips). The
goal is to set accurate expectations before you swap loaders, not to claim a
win.
Where a Vercel/Next.js behaviour isn’t explicitly documented in their public
docs, the column is marked ? rather than guessed.
| Format | Next.js default | edgesharp | Notes |
|---|
| JPEG (baseline-sequential) | ✓ | ✓ | Decoded by the in-Zig decoder (jpeg.zig). |
| JPEG (progressive) | ✓ | ✓ | Decoded by the vendored stb_image.h decoder (public-domain, single-file C). Same RGBA output as the baseline path; same resize and encode pipeline downstream. |
| JPEG (CMYK colorspace) | ✓ | ✗ | Rare on the web; design choice. File an issue if you need it. |
| PNG (8-bit RGBA) | ✓ | ✓ | |
| PNG (16-bit) | ✓ | ✗ | Uncommon; design choice. |
| GIF (still) | ✓ | ✓ | Re-encoded as JPEG/WebP/AVIF. |
| GIF (animated) | ✓ passthrough | ✓ passthrough | Source bytes returned unchanged. |
| WebP (still) | ✓ | ✓ | |
| WebP (animated) | ✓ passthrough | ✓ passthrough | Source bytes returned unchanged. |
| AVIF | ✓ | ✓ | edgesharp uses a vendored libavif build; kill switch via DISABLED_FORMATS="avif". |
| SVG | ✓ (sanitized) | ✓ (passthrough + CSP/sandbox) | Both serve SVG without re-encoding. Next.js sanitizes; edgesharp returns the source bytes with Content-Security-Policy: script-src 'none'; sandbox; which neutralizes embedded scripts in the browser. |
| TIFF | ✓ | ✗ | Out of scope (web-image use case). |
| HEIC / HEIF | ? | ✗ | Out of scope. |
| RAW (CR2, NEF, ARW, …) | ✗ | ✗ | Out of scope on both. |
| BMP | ✓ | ✗ | Rare; design choice. |
| ICO | ✓ | ✗ | Rare; design choice. |
| Format | Next.js default | edgesharp | Notes |
|---|
| JPEG (baseline) | ✓ | ✓ | |
| JPEG (progressive) | ? | ✗ | Most outputs are baseline; progressive output requires a multi-scan encoder. |
| PNG | ✓ | ✓ | |
| WebP | ✓ | ✓ | |
| AVIF | ✓ | ✓ | |
These are Next.js component-level features. edgesharp only changes the
loaderFile, so anything Next.js does on the client side is unaffected.
| Feature | Next.js default | edgesharp | Notes |
|---|
srcSet generation from deviceSizes / imageSizes | ✓ | ✓ | Identical, same defaults. |
sizes attribute for responsive images | ✓ | ✓ | |
priority / loading="eager" | ✓ | ✓ | |
| Lazy loading | ✓ | ✓ | |
fill mode | ✓ | ✓ | |
Blur preview via blurDataURL | ✓ | ✓ | Next.js generates blurDataURL at build time; not affected by the loader. |
Static export (output: 'export') | ✓ | ✓ | edgesharp bakes the Worker URL into every srcSet at build time. |
| EXIF orientation auto-rotate (mobile portraits) | ✓ | ✓ | Both rotate based on EXIF tag 0x0112. |
| Behavior | Next.js default | edgesharp | Notes |
|---|
| Quality range | 1–100 | 1–100 | Default 75 on both. |
| Width allowlist | derived from deviceSizes+imageSizes | same | edgesharp validates against the same Next.js defaults. |
?dpr=1|2|3 density multiplier | ? | ✓ | edgesharp accepts dpr and clamps to MAX_WIDTH after multiplication. |
ETag / 304 Not Modified | ✓ | ✓ | edgesharp’s ETag is a strong validator derived from (imageUrl, w, q, format). |
Vary: Accept | ✓ | ✓ | |
Cache-Control: public, max-age=31536000, immutable | ✓ | ✓ | |
Content-Disposition: inline | ✓ | ✓ | |
X-Content-Type-Options: nosniff | ✓ | ✓ | |
| Restrictive CSP on output | ? | ✓ script-src 'none'; sandbox; | |
| Unsafe content-type rejection | ✓ | ✓ | |
These are runtime knobs edgesharp adds for self-hosted operators. Vercel’s
hosted image optimization is largely zero-config and doesn’t expose
equivalent first-class flags.
| Control | Next.js / Vercel | edgesharp | Notes |
|---|
| URL allowlist for upstream image hosts | images.remotePatterns | ALLOWED_ORIGINS | edgesharp accepts "*" as well, useful for demos, not for production. |
| Caller allowlist (Referer / Origin) | ✗ | ALLOWED_REFERERS | Stops other sites hotlinking your Worker. |
Hard cap on ?q= | ✗ | MAX_QUALITY | Cost protection against expensive q=100 requests. |
| Format kill switch | ✗ | DISABLED_FORMATS (CSV: jpeg, png, webp, avif, gif, svg) | Drop transformed outputs (negotiator picks next-best the browser accepts) or passthrough inputs (Worker returns 415). |
| Backend pluggability | ✗ | IMAGE_BACKEND | Can route every transform through Cloudflare Images instead of WASM. |
| Next.js / Vercel | edgesharp |
|---|
| Source available | partial (loader API documented) | ✓ MIT, GitHub |
| Run on your own infrastructure | self-host Next.js, but the optimizer ships with the framework | ✓ Cloudflare Workers + R2 in your account |
| Deploy time | n/a (managed) | One-click Deploy to Cloudflare |
- Latency comparison. Neither party publishes a latency SLO for image
optimization, and synthetic benchmarks on
wrangler dev don’t reflect edge
network behavior. The numbers in Performance are
local-machine measurements, directional, not a SLO.
- Quality / compression ratio. Visual conformance against Sharp passes at
PSNR ≥ 30 dB (visually indistinguishable). Output file sizes vary 0–10%
vs Sharp depending on format and content. See
Conformance for the test harness.