CatSVG

CatSVG is a placeholder image service that draws cats. Ask for any size and any seed word and you get a cat: generated as SVG on the fly, a few kilobytes on the wire, sharp at any resolution, and identical every time that URL is requested.

Use it anywhere

• HTML<img src="https://catsvg.app/cat/1200x300/mackerel.svg" width="1200" height="300" alt="Cat placeholder" />
• Markdown![Cat placeholder](https://catsvg.app/cat/800x450/biscuit.svg)
• CSSbackground-image: url("https://catsvg.app/cat/1200x600/pebble.svg");
• Postcard<img src="https://catsvg.app/cat/postcard/900x600/mackerel.svg" width="900" height="600" alt="A postcard from a cat" />
• Avatar<img src="https://catsvg.app/cat/96/${userId}.svg" width="96" height="96" alt="Avatar" />

URL API

URL	What you get
/cat/mackerel.svg	Seeded cat, 400×400.
/cat/240/mackerel.svg	Square at 240px.
/cat/1200x300/mackerel.svg	Any width×height up to 2000.
/cat/320x320/random.svg	A different cat every request (never cached).
/cat/400?seed=biscuit	Query form — same thing.
/cat/postcard/mackerel.svg	The same cat as a postcard, 600×400.
/cat/postcard/back/900x600/mackerel.svg	The written side: message, stamp, postmark.

Query parameters

Param	Effect
seed	Any string. Same seed always returns the same cat.
w, h	Size override, 16–2000px.
preset	anything · minimal · maximal · noir · pastel · feral
mode	cat (default) or postcard.
side	front or back — the two sides of a postcard.
text	Caption pill on a cat; the greeting or message on a postcard.
to, from	Addressee and signature on a postcard back.
caption	Small line under the greeting on a postcard front.
postmark	Words in the postmark ring.
stamp	How many stamps frank the back, 0–5. Default 1.
brand	brand=off drops every CatSVG mark.
<trait>	Pin one trait: eyes=star, palette=neon, body=loaf, …

Examples

Questions

What is CatSVG?

A placeholder image service that draws cats. Every URL — say /cat/1200x300/mackerel.svg — is turned into one specific cat and rendered as SVG on the fly. No image files are stored and nothing is fetched from anywhere else.

How do I use a cat placeholder image?

Point an <img> at it: <img src="https://catsvg.app/cat/1200x300/mackerel.svg" />. The size segment is optional and so is the .svg suffix, so https://catsvg.app/cat/mackerel works too.

Will the same URL always give me the same cat?

Yes. A cat is a pure function of its URL, so seeded cats are served immutable and cached for a year. The one exception is the seed "random", which rolls a fresh cat on every request and is never cached.

Do I need an API key or an account?

No. The image endpoint is public, sends Access-Control-Allow-Origin: *, and needs no key, token or signup.

Can I use the cats commercially?

Yes. CatSVG is MIT licensed, and a generated cat is plain SVG with no third-party artwork in it — put it in a client mockup, a product screenshot or a shipped page, no attribution required.

Is this a PlaceKitten alternative?

Same job, different method. PlaceKitten serves photographs of cats; CatSVG draws each cat as vector artwork from the URL, so a placeholder is a few kilobytes, stays sharp on any display, and the same URL always returns the same cat.

What sizes and aspect ratios work?

Anything from 16 to 2000 pixels on each side. Wide and tall requests extend the scene around the cat instead of cropping it, so a 1200×300 banner still shows a whole cat.

Can I use the cats as avatars?

Yes. Pass a user id, username or email hash as the seed and every person gets their own stable cat, the way an identicon works — but a cat.

What is postcard mode?

Postcard mode mounts the same generated cat on a paper card. /cat/postcard/mackerel.svg is the picture side — the cat in a window with a greeting printed under it — and /cat/postcard/back/mackerel.svg is the written side, with a message, a stamp carrying a miniature of the same cat, a postmark and the address rules. Add ?text=… to write the greeting or the message yourself; leave it off and the cat writes its own.

Can I put my own words on a postcard?

Yes, every field on the card is a query parameter: ?text= is the greeting on the front and the message on the back, ?caption= is the small print under the greeting, ?to= and ?from= are the addressee and the signature, and ?postmark= sets the words in the postmark ring. Anything you leave out, the cat writes itself from the seed. ?stamp= sets how many stamps frank the back — none, one, or up to five in a row — and ?brand=off removes every CatSVG mark, which is what you want if you are printing the card for real.

Can I run CatSVG myself?

Yes. The whole thing is open source on GitHub: the generator is a dependency-free TypeScript module and the service is a single function you can host anywhere.