Font subset

POST /api/font-subset2 quota units per call · cache hits free

Strip a font to only the Unicode codepoints you need — the standard web-perf optimization for self-hosted fonts. Ranges, U+ syntax, and literal characters supported.

Strips a TTF/OTF down to only the glyphs needed for a given set of Unicode codepoints — the standard web-perf optimization for self-hosted fonts. Output keeps the same format as the input. The `codepoints` field accepts a permissive spec: - Literal characters: `Hello,World!` - ASCII ranges: `A-Z,a-z,0-9` - Hex codepoints: `U+0041`, `U+0041-U+005A` - Mixed: `A-Za-z0-9.,U+2014U+2026` (em-dash, ellipsis) Typical use: ship a 4 KB Latin-only subset instead of a 200 KB full-Unicode font for marketing landing pages.

Inputs

Name	Type	Default	Description
font*	file	—	TTF or OTF font.
codepoints*	string	—	Codepoint spec — literal chars, ASCII ranges (A-Z, 0-9), and U+XXXX[-U+YYYY] ranges. Whitespace and commas are separators.

Response

Modes: binary, json. Cache: yes (24h TTL).

Every response carries x-cache (HIT / MISS / BYPASS), x-cache-signature (stable across identical inputs), and the rate-limit headers listed below.

Quota & limits

Cost per call	2 units against the 10,000-unit monthly quota. Cache hits are free — only cache misses decrement.
Burst limit	200 requests per rolling minute, shared across all tools.
Max request size	`10 MiB` (base64 inflates file payloads ~33% — the limit applies to the decoded bytes).
Max response size	`10 MiB`
Timeout	15s wall clock.
Rate-limit headers	`X-RateLimit-Limit`, `X-RateLimit-Remaining`, `X-RateLimit-Burst-Limit` on every response; `X-Quota-Warning` once 80% of the monthly quota is spent; `Retry-After` on 429s.

Errors

Errors are JSON with an error string; schema failures add a details object (Zod's flattened field errors).

Status	When	Body
400	Input fails the tool's schema (wrong type, missing required field, malformed base64) or the file bytes can't be parsed as the expected format.	{ "error": "invalid inputs", "details": { "fieldErrors": { … } } }
401	Missing or invalid X-Api-Key / X-Account-Id headers (or no session when called from the browser).	{ "error": "unauthorized" }
404	Unknown tool id, or calling /api/* on the website hostname instead of api.xtract.bot.	{ "error": "not found" }
413	Request body over the tool's max request size, or an image header declaring more megapixels than the tool's pixel budget.	{ "error": "…exceeds maxRequestBytes…" }
415	Content-Type isn't application/json on the json-body transport.	{ "error": "unsupported content-type; expected application/json" }
429	Monthly quota or the 200/min burst limit exhausted. Check Retry-After and the X-RateLimit-* headers.	{ "error": "monthly quota exceeded", "monthRemaining": 0, … }
5xx	Conversion engine failure. Safe to retry; if it persists, the input is hitting a bug — please report it.	{ "error": "…" }

Code samples

Built from the ascii-letters example.

# Download or substitute the example input:
#   curl -O https://xtract.bot/examples/font-info/DejaVuSansMono.ttf
FONT=$(base64 -w0 < DejaVuSansMono.ttf)

curl -X POST https://api.xtract.bot/api/font-subset \
  -H "Content-Type: application/json" \
  -H "Accept: application/octet-stream" \
  -H "X-Account-Id: $XTRACT_ACCOUNT_ID" \
  -H "X-Api-Key: $XTRACT_API_KEY" \
  -d '{
  "codepoints": "A-Z,a-z",
  "font": "'"$FONT"'"
}'