FormForge API

FormForge converts JSON form definitions into beautiful, self-contained HTML forms with built-in CSS, client-side validation, and accessible markup. The API requires no SDK — just a single POST request.

Base URL: https://formforge-api.vercel.app

Version: 1.0.0 | Format: JSON over HTTPS

Try it free: The API allows 20 forms per day without an API key. Sign up for a free key to track usage and unlock more quota.

Authentication

Pass your API key in the Authorization header using Bearer scheme:

http

Authorization: Bearer ff_live_your_api_key_here

Alternatively, use the X-Api-Key header for legacy clients. Keys always start with ff_live_ (live) or ff_test_ (test).

Unauthenticated requests are allowed on the free anonymous tier (20 forms/day per IP).

Error Responses

All errors return a JSON object with error, code, and an optional details field.

json

{
  "error": "The 'fields' array is required.",
  "code":  "INVALID_INPUT"
}

Code	HTTP	Description
INVALID_INPUT	400	Bad request body or missing required field
PARSE_ERROR	400	Request body is not valid JSON
UNAUTHORIZED	401	API key missing, invalid, or inactive
RATE_LIMITED	429	Daily form limit exceeded for your tier
INPUT_TOO_LARGE	413	Request body exceeds your tier's size limit
INTERNAL_ERROR	500	Server-side rendering error

Rate Limits

Limits reset at midnight UTC. Authenticated requests return rate-limit headers on every response:

http

X-RateLimit-Limit:     20
X-RateLimit-Remaining: 17
X-RateLimit-Reset:     1740787200

Tier	Forms/day	Input limit	Price
Free (anonymous)	20	50 KB	$0
Free (keyed)	20	50 KB	$0
Builder	300	512 KB	$14/mo
Enterprise	Unlimited	5 MB	$39/mo

POST /api/json-to-form

Accepts a JSON form schema and returns a complete, self-contained HTML document with embedded CSS, client-side validation, and submit handling.

Request body

Field	Type	Description
fieldsrequired	array	Array of field definition objects (1–100 items). See Field Schema.
titleoptional	string	Form heading displayed above the fields.
descriptionoptional	string	Subtitle text below the title.
themeoptional	string	`modern` \| `corporate` \| `playful`. Default: `modern`.
submitUrloptional	string	URL to POST the form data to. If omitted, the form shows a success message on submit without making an HTTP request.
submitLabeloptional	string	Label on the submit button. Default: `Submit`.
methodoptional	string	`GET` \| `POST`. Default: `POST`.
showRequiredoptional	boolean	Show asterisk on required fields. Default: `true`.

Responses

200 Form rendered successfully

json

{
  "html": "<!DOCTYPE html>\n<html lang=\"en\">...",
  "meta": {
    "theme":      "modern",
    "fieldCount": 3,
    "fieldTypes": ["email", "text", "textarea"],
    "title":      "Contact Us",
    "generatedAt": "2026-02-28T12:00:00.000Z"
  }
}

400Invalid schema

401Invalid API key

413Request too large for tier

429Rate limit exceeded

Try it out

Request body (JSON)

POST /api/signup

Creates a new free-tier API key for the provided email address. The plain-text key is returned once and cannot be retrieved again.

Request body

Field	Type	Description
emailrequired	string	Valid email address. Maximum 3 active keys per address.

Responses

201Key created

json

{
  "message":  "API key created successfully. Save this key — it will not be shown again.",
  "api_key":  "ff_live_xxxxxxxxxxxxxxxxxxxxxxxxxxxx",
  "tier":     "free",
  "email":    "you@example.com",
  "rate_limit": {
    "forms_per_day":  20,
    "max_input_bytes": 51200
  }
}

400Invalid email

409Max keys per email reached (3)

Field Schema

Each item in the fields array supports the following properties:

Property	Type	Description
namerequired	string	Unique field identifier used as the HTML `name` attribute.
typerequired	string	Field type. See Field Types.
labelrequired	string	Human-readable label displayed above the field.
required	boolean	If true, the field is validated as non-empty on submit.
placeholder	string	Placeholder text inside the input (not for checkbox/radio).
helpText	string	Small helper text shown below the field.
options	string[]	Required for `select` and `radio`. Optional for checkbox (creates a multi-select group).
value	string	Default/pre-filled value.
min / max	number\|string	Min/max value for `number` and `date` fields.
minLength / maxLength	number	Character limits for `text` and `textarea`.
pattern	string	Regex pattern for custom input validation.
disabled	boolean	Renders the field in a disabled state.
readonly	boolean	Renders the field as read-only.
autocomplete	string	HTML autocomplete hint (e.g. `email`, `name`).

Themes

The theme property controls the visual style of the generated form. All themes are self-contained CSS — no external fonts or stylesheets are loaded.

Theme	Description	Accent color
modern	Clean, minimal. System sans-serif font, 8px border radius. Good default for most products.	#10b981 (emerald)
corporate	Professional blue. Tighter radius, bold labels. Suitable for B2B and SaaS dashboards.	#1d4ed8 (blue)
playful	Rounded, colorful. Cursive font stack, large radius, purple accent. Great for consumer apps.	#8b5cf6 (violet)

Field Types

Type	HTML element	Notes
text	<input type="text">	Supports minLength, maxLength, pattern
email	<input type="email">	Validates email format on blur and submit
number	<input type="number">	Supports min, max
textarea	<textarea>	Resizable. Supports minLength, maxLength
select	<select>	Requires options array. Renders a blank placeholder option
checkbox	<input type="checkbox">	No options: single toggle. With options: multi-select group
radio	<input type="radio">	Requires options array. Single-select group
date	<input type="date">	Browser date picker. Supports min, max as YYYY-MM-DD strings
tel	<input type="tel">	Validates phone number format
url	<input type="url">	Validates URL format (requires https://)