Developer Documentation

API Reference

Integrate 200+ conversion and utility tools into your applications with our simple RESTful API.

Get API Key

Create one in your dashboard

Authenticate

Add Bearer token to headers

Make Requests

Call any endpoint below

Go Live

All tools are free to use

Authentication

All API requests require authentication via a Bearer token in the Authorization header. You can generate API keys from your Dashboard.

Authorization: Bearer fct_your_api_key_here

Base URL

https://api.freeconvertingtools.com/v1

Rate Limits & Credits

Each API call consumes credits based on the endpoint. Rate limits are enforced per API key. Exceeding limits returns 429 Too Many Requests.

Plan	Price	Credits	Rate Limit
Free	$0	100/day	10 req/min
API Starter	$9/mo	5,000/mo	60 req/min
API Pro	$29/mo	50,000/mo	200 req/min
Enterprise	Custom	Unlimited	Custom

Endpoints

POST/convert/image2 credits/call

Convert an image between formats (PNG, JPG, WebP, AVIF, GIF, TIFF, BMP) with resize, quality, lossless mode, and metadata control.

Parameters

Name	Type	Required	Description
`file`	File	Yes	The image file to convert (multipart/form-data)
`outputFormat`	string	Yes	Target format: png, jpg, webp, avif, gif, tiff, bmp
`quality`	number	No	Output quality 1-100 (default: 90). For lossy formats (JPG, WebP, AVIF).
`width`	number	No	Target width in pixels (1-10000).
`height`	number	No	Target height in pixels (1-10000).
`fit`	string	No	How image fits: cover, contain, fill, inside (default), outside.
`background`	string	No	Background color for transparent areas (hex, default: #ffffff).
`lossless`	boolean	No	Lossless mode for WebP/AVIF (default: false).
`stripMetadata`	boolean	No	Remove EXIF/metadata from output (default: false).

Example Request

curl -X POST https://api.freeconvertingtools.com/v1/convert/image \
  -H "Authorization: Bearer fct_your_api_key" \
  -F "file=@photo.png" \
  -F "output_format=webp" \
  -F "quality=85" \
  -o converted.webp

Response

Binary file (the converted image)

POST/convert/text1 credit/call

Convert text/data between formats (JSON, CSV, XML, YAML, Base64, URL encoding).

Parameters

Name	Type	Required	Description
`input`	string	Yes	The input text to convert
`from_format`	string	Yes	Source format: json, csv, xml, yaml, base64, url, markdown, html
`to_format`	string	Yes	Target format: json, csv, xml, yaml, base64, url, markdown, html

Example Request

curl -X POST https://api.freeconvertingtools.com/v1/convert/text \
  -H "Authorization: Bearer fct_your_api_key" \
  -H "Content-Type: application/json" \
  -d '{"input": "name,age\nJohn,30", "from_format": "csv", "to_format": "json"}'

Response

{
  "success": true,
  "result": "[{\"name\":\"John\",\"age\":\"30\"}]",
  "credits_used": 1
}

POST/tools/hash1 credit/call

Generate hash digests of text input (MD5, SHA-1, SHA-256, SHA-512).

Parameters

Name	Type	Required	Description
`input`	string	Yes	The text to hash
`algorithm`	string	No	Hash algorithm: md5, sha1, sha256 (default), sha512

Example Request

curl -X POST https://api.freeconvertingtools.com/v1/tools/hash \
  -H "Authorization: Bearer fct_your_api_key" \
  -H "Content-Type: application/json" \
  -d '{"input": "Hello World", "algorithm": "sha256"}'

Response

{
  "success": true,
  "hash": "a591a6d40bf420404a011733cfb7b190d62c65bf0bcda32b57b277d9ad9f146e",
  "algorithm": "sha256",
  "credits_used": 1
}

POST/tools/qr-code1 credit/call

Generate a QR code image from text or URL.

Parameters

Name	Type	Required	Description
`content`	string	Yes	The text or URL to encode
`size`	number	No	Output size in pixels (default: 300, max: 1000)
`format`	string	No	Output format: png (default), svg
`color`	string	No	Foreground color as hex (default: #000000)
`background`	string	No	Background color as hex (default: #FFFFFF)

Example Request

curl -X POST https://api.freeconvertingtools.com/v1/tools/qr-code \
  -H "Authorization: Bearer fct_your_api_key" \
  -H "Content-Type: application/json" \
  -d '{"content": "https://freeconvertingtools.com", "size": 500}' \
  -o qr.png

Response

Binary file (PNG or SVG image)

POST/tools/password1 credit/call

Generate a cryptographically secure password or passphrase.

Parameters

Name	Type	Required	Description
`length`	number	No	Password length (default: 16, max: 128)
`type`	string	No	Type: password (default), passphrase
`uppercase`	boolean	No	Include uppercase letters (default: true)
`numbers`	boolean	No	Include numbers (default: true)
`symbols`	boolean	No	Include symbols (default: true)

Example Request

curl -X POST https://api.freeconvertingtools.com/v1/tools/password \
  -H "Authorization: Bearer fct_your_api_key" \
  -H "Content-Type: application/json" \
  -d '{"length": 24, "type": "password"}'

Response

{
  "success": true,
  "password": "Xk9#mQ2&vL5@nR8!pW3$jH6",
  "strength": "very_strong",
  "entropy_bits": 157,
  "credits_used": 1
}

POST/tools/text1 credit/call

Transform text with various operations (uppercase, lowercase, titlecase, reverse, base64, URL/HTML encode/decode, slug, count).

Parameters

Name	Type	Required	Description
`text`	string	Yes	The input text to transform
`operation`	string	Yes	Operation: uppercase, lowercase, titlecase, reverse, base64-encode, base64-decode, url-encode, url-decode, html-encode, html-decode, slug, remove-whitespace, count

Example Request

curl -X POST https://api.freeconvertingtools.com/v1/tools/text \\
  -H "Authorization: Bearer fct_your_api_key" \\
  -H "Content-Type: application/json" \\
  -d '{"text": "Hello World", "operation": "uppercase"}'

Response

{
  "success": true,
  "operation": "uppercase",
  "result": "HELLO WORLD"
}

POST/tools/calculator1 credit/call

Multi-purpose calculator API: BMI, percentage, compound interest, unit conversion, age calculation.

Parameters

Name	Type	Required	Description
`type`	string	Yes	Calculator type: bmi, percentage, compound-interest, unit-convert, age
`weight_kg`	number	No	Weight in kg (for BMI)
`height_cm`	number	No	Height in cm (for BMI)
`value`	number	No	Input value (for percentage, unit-convert)
`principal`	number	No	Starting amount (for compound interest)
`rate`	number	No	Annual interest rate (for compound interest)
`years`	number	No	Number of years (for compound interest)
`from`	string	No	Source unit: km, mi, kg, lb, c, f, m, ft, l, gal
`to`	string	No	Target unit: same options as from
`birthdate`	string	No	Birthdate YYYY-MM-DD (for age)

Example Request

curl -X POST https://api.freeconvertingtools.com/v1/tools/calculator \\
  -H "Authorization: Bearer fct_your_api_key" \\
  -H "Content-Type: application/json" \\
  -d '{"type": "bmi", "weight_kg": 70, "height_cm": 175}'

Response

{
  "success": true,
  "type": "bmi",
  "result": { "bmi": 22.86, "category": "Normal" }
}

POST/tools/text-process1 credit/call

Advanced text processing: extract emails/URLs, remove duplicates, sort lines, find/replace, diff, lorem ipsum.

Parameters

Name	Type	Required	Description
`operation`	string	Yes	Operation: extract-emails, extract-urls, remove-duplicates, sort-lines, find-replace, diff, lorem-ipsum
`text`	string	No	Input text (required for most operations)
`text1`	string	No	First text (for diff)
`text2`	string	No	Second text (for diff)
`find`	string	No	Search string (for find-replace)
`replace`	string	No	Replacement string (for find-replace)
`paragraphs`	number	No	Number of paragraphs (for lorem-ipsum, default: 3)

Example Request

curl -X POST https://api.freeconvertingtools.com/v1/tools/text-process \\
  -H "Authorization: Bearer fct_your_api_key" \\
  -H "Content-Type: application/json" \\
  -d '{"operation": "extract-emails", "text": "Contact us at hello@example.com or support@test.org"}'

Response

{
  "success": true,
  "operation": "extract-emails",
  "count": 2,
  "results": ["hello@example.com", "support@test.org"]
}

GET/me

Get your account info, current plan, and remaining credits.

Example Request

curl https://api.freeconvertingtools.com/v1/me \
  -H "Authorization: Bearer fct_your_api_key"

Response

{
  "email": "you@example.com",
  "plan": "api_starter",
  "credits_remaining": 4850,
  "credits_used_today": 150,
  "rate_limit_per_minute": 60,
  "keys_count": 2
}

Error Codes

Code	Meaning	Resolution
`400`	Bad Request	Check your parameters. A required field may be missing.
`401`	Unauthorized	Verify your API key is correct and active.
`403`	Forbidden	Your plan may not have access to this endpoint.
`404`	Not Found	Verify the endpoint path is correct.
`413`	Payload Too Large	File exceeds the maximum size limit (50MB).
`429`	Too Many Requests	Rate limit exceeded. Wait and retry with exponential backoff.
`500`	Internal Server Error	Server error. Contact support if it persists.

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