Parameters

All transform parameters are optional; out-of-range values are clamped, not rejected.

Param	Type	Range / values	Default	Description
`project`	string	—	required	Project id (allowlist gates access)
`sig`	string	base64url HMAC-SHA256	required when the project enables signed URLs	Request signature over the source URL + sorted params
`kid`	int	current project key version	required for signed URLs	Invalidates old URL generations after secret rotation
`iat` / `exp`	Unix seconds	project signing policy	required when a signing lifetime is configured	Signed issuance and expiration timestamps
`url`	URL	absolute `http`/`https` URL	—	Source image URL when not using the `/img/<source-url>` path form
`w` / `h`	int or `auto` for `w`	1–5000	bounded original	Target width/height; `w=auto` resolves `Sec-CH-Width`, then `Sec-CH-Viewport-Width`
`resize` / `s`	string	`WIDTHxHEIGHT`, `WIDTH`, `xHEIGHT`	—	Compact size alias; explicit `w`/`h` win
`q`	int	30–100	project default	Output quality
`fmt`	enum	`auto` `avif` `webp` `jpeg` `png` `gif` `heif` `tiff` `svg`	`auto`	Output format (`auto` negotiates AVIF/WebP/JPEG)
`fit`	enum	`cover` `contain` `fill` `inside` `outside`	`cover`	How to fit the `w`×`h` box
`position` / `pos` / `gravity`	enum	edges, corners, compass gravities, `entropy`, `attention`	`centre`	Crop anchor for `cover`/`contain`
`dpr`	number or `auto`	1–3	`1`	Device pixel ratio; `auto` resolves the `Sec-CH-DPR` Client Hint
`enlarge`	bool	`1` `true` `yes` `on`	`false`	Allow upscaling past source dimensions
`kernel`	enum	`nearest` `linear` `cubic` `mitchell` `lanczos2` `lanczos3` `mks2013` `mks2021`	`lanczos3`	Resize kernel
`background` / `bg`	color	Sharp color string	—	Fill color for `contain`, `flatten`, `extend`, and arbitrary rotate
`flatten`	bool	`1` `true` `yes` `on`	`false`	Merge alpha onto `background`
`extract` / `crop`	string	`left,top,width,height`	—	Crop an exact source rectangle before resize
`trim`	bool/int	`true` or 0–255	`false`	Trim matching edges; number is threshold
`extend`	string	`all`, `y,x`, `top,right,bottom,left`	—	Add output padding after resize
`extendWith`	enum	`background` `copy` `repeat` `mirror`	`background`	Fill mode for `extend`
`rotate` / `r`	float	-360–360	—	Rotate by degrees after EXIF auto-orient
`flip` / `flop`	bool	`1` `true` `yes` `on`	`false`	Vertical / horizontal mirror
`blur`	int	0–1000	`0`	Gaussian blur sigma
`sharpen`	bool/float	`true` or 0.000001–10	`false`	Apply mild or sigma-based sharpening
`median`	int	1–25	—	Median filter size
`gamma` / `gammaOut`	float	1–3	—	Gamma correction
`negate`	bool	`1` `true` `yes` `on`	`false`	Invert colors
`normalize` / `normalise`	bool	`1` `true` `yes` `on`	`false`	Contrast normalization
`threshold`	int	0–255	—	Convert to black/white threshold
`brightness` / `saturation`	float	0–10	—	Modulate brightness/saturation
`hue`	int	-360–360	—	Hue rotation
`lightness`	float	-100–100	—	Lightness adjustment
`tint`	color	Sharp color string	—	Apply a tint
`grayscale` / `greyscale`	bool	`1` `true` `yes` `on`	`false`	Convert to grayscale
`animated` / `a`	bool	`1` `true` `yes` `on`	`false`	Preserve animated GIF/WebP frames when output supports it

Notes

No upscaling by default. Keenpix never enlarges past the source resolution unless enlarge=1 is set.
Source URL. Put the absolute source URL after /img/, for example /img/https://cdn.example.com/hero.jpg?project=ID&w=1200, or send it as /img/?url=https%3A%2F%2Fcdn.example.com%2Fhero.jpg&project=ID&w=1200.
dpr multiplies the target dimensions — w=400&dpr=2 renders at 800px.
Client Hints. w=auto&dpr=auto lets the browser provide Width or Sec-CH-Viewport-Width plus Sec-CH-DPR. Sec-CH-Width is already in device pixels, so Keenpix converts it back to a logical width before applying DPR and avoids double scaling. Keenpix advertises and varies by all three current headers; the older unprefixed forms are accepted for compatibility. Automatic widths and DPRs are rounded to a bounded shared ladder so a signed auto URL cannot be turned into unlimited cache variants by spoofing headers. Explicit numeric values remain best for deterministic prewarming.
fmt=auto depends on the project's Auto-format setting; when off, auto serves JPEG. Omitting fmt is treated as auto. It is raster negotiation only: SVG origins are rasterized and returned as AVIF, WebP, or JPEG rather than preserved as SVG. An explicit fmt is always honoured and disables browser negotiation for that request. Use explicit fmt values when your CDN cannot cache separate variants by Accept.
Framework format props. Image frameworks often map format="avif" or format="webp" directly to fmt=avif or fmt=webp. Leave those props unset when you want Keenpix to return AVIF or WebP based on browser support.
fmt=svg is explicit only. It returns image/svg+xml only for SVG origins, optimizes them through SVGO, and strips active content. Raster transform modifiers do not apply to SVG output.
q defaults to the project's Default quality (Settings → Pipeline).
Watermarks are project configuration, not public query parameters. Configure the asset, opacity, scale, position, and margin under Settings → Pipeline. The asset host must be allowlisted. Raster variants receive the overlay; explicit SVG output remains optimized SVG without raster compositing.

position=attention and position=entropy currently expose Sharp/libvips crop heuristics. A dedicated Keenpix subject-aware smart crop is deliberately not part of v0.3 yet. Its focal-point model, face/object behavior, privacy implications, fallbacks, and cache identity need a separate design study before implementation. Named transform presets are also intentionally outside this release.

Notes

Smart-crop research TODO

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