API Documentation

Build with DevDiagrams.

The DevDiagrams API lets you generate syntax diagrams programmatically from your own applications, scripts, and CI pipelines. API access requires a Professional subscription.

Getting started

Three steps to your first diagram.

1. Get a Professional subscription
API access requires a Professional subscription. View pricing →

2. Generate an API key
Go to your Account page and generate an API key in the API Keys section. Copy the key immediately — it won't be shown again.

3. Make your first request
Include your API key in the


                    X-Api-Key

header of every request.

Example request — curl

curl -X POST https://devdiagrams.com/api/SyntaxDiagram/Render \ -H "X-Api-Key: your_api_key_here" \ -H "Content-Type: application/json" \ -d '{ "grammarText": "expr : term (\"+\" term | \"-\" term)* ;", "grammarSyntax": "antlr" }'

Authentication

API key authentication.

All API requests must include your API key in the X-Api-Key header. Keys can be generated and revoked from your Account page. You can have up to 10 active API keys at a time.

Header

X-Api-Key: dd_your_api_key_here

Keep your API keys secure. Do not commit them to source control or expose them in client-side code. If a key is compromised, revoke it immediately from your Account page and generate a new one.

Base URL

All requests go here.

Base URL

https://devdiagrams.com/api

Endpoints

Available API endpoints.

POST /api/SyntaxDiagram/Render Render a syntax diagram

Request body

Field	Type	Required	Description
grammarText	string	required	The grammar text to render. Supports ANTLR4 and BNF syntax.
grammarSyntax	string	optional	The grammar format. Valid values: `antlr`, `bnf`. If not specified, your saved preference is used.

Response — 200 OK

Field	Type	Description
rules	array	Array of rendered diagram rules.
rules[].name	string	The rule name.
rules[].svg	string	The rendered SVG diagram as an HTML string.
rules[].ruleText	string	The original grammar text for this rule.
rules[].references	string[]	Names of rules this rule references.
rules[].description	string	Description extracted from comments above the rule, if present.
errors	string[]	Any errors encountered during rendering. Empty on success.

Example response

{ "rules": [ { "name": "expr", "svg": "<svg ...>...</svg>", "ruleText": "expr : term (\"+\" term | \"-\" term)* ;", "references": ["term"], "description": "" } ], "errors": [] }

Response headers

Header	Description
X-RateLimit-Limit	Maximum requests allowed per day.
X-RateLimit-Remaining	Requests remaining today.
X-RateLimit-Reset	UTC timestamp when the daily limit resets (midnight UTC).

Error codes

What went wrong.

All error responses use the following format:

Error response format

{ "error": "Human-readable error message.", "code": "ERROR_CODE" }

Status	Code	Description
400	MISSING_GRAMMAR_TEXT	The grammarText field is missing or empty.
400	INVALID_GRAMMAR_SYNTAX	The grammarSyntax value is not recognized. Valid values are antlr and bnf.
401	MISSING_API_KEY	The X-Api-Key header is missing from the request.
401	INVALID_API_KEY	The provided API key is invalid or has been revoked.
403	INSUFFICIENT_TIER	API access requires a Professional subscription.
429	RATE_LIMIT_EXCEEDED	The daily request limit of 1000 has been exceeded. Resets at midnight UTC.
500	—	An unexpected server error occurred. Please try again.

Rate limiting

1000 requests per day.

API usage is limited to 1000 requests per day per API key. The limit resets at midnight UTC. Monitor your usage with the X-RateLimit-Remaining response header. When the limit is exceeded you will receive a 429 response until the limit resets.

Try the API in your browser.

Open Swagger UI →