Writer & Humanizer

curl --request POST \
  --url https://www.stealthgpt.ai/api/stealthify \
  --header 'Content-Type: application/json' \
  --header 'api-token: <api-token>' \
  --data '
{
  "prompt": "<string>",
  "rephrase": true,
  "model": "<string>",
  "tone": "<string>",
  "writingMode": "<string>",
  "qualityMode": "<string>",
  "outputFormat": "<string>"
}
'

import requests

url = "https://www.stealthgpt.ai/api/stealthify"

payload = {
    "prompt": "<string>",
    "rephrase": True,
    "model": "<string>",
    "tone": "<string>",
    "writingMode": "<string>",
    "qualityMode": "<string>",
    "outputFormat": "<string>"
}
headers = {
    "api-token": "<api-token>",
    "Content-Type": "application/json"
}

response = requests.post(url, json=payload, headers=headers)

print(response.text)

const options = {
  method: 'POST',
  headers: {'api-token': '<api-token>', 'Content-Type': 'application/json'},
  body: JSON.stringify({
    prompt: '<string>',
    rephrase: true,
    model: '<string>',
    tone: '<string>',
    writingMode: '<string>',
    qualityMode: '<string>',
    outputFormat: '<string>'
  })
};

fetch('https://www.stealthgpt.ai/api/stealthify', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://www.stealthgpt.ai/api/stealthify",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => json_encode([
    'prompt' => '<string>',
    'rephrase' => true,
    'model' => '<string>',
    'tone' => '<string>',
    'writingMode' => '<string>',
    'qualityMode' => '<string>',
    'outputFormat' => '<string>'
  ]),
  CURLOPT_HTTPHEADER => [
    "Content-Type: application/json",
    "api-token: <api-token>"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://www.stealthgpt.ai/api/stealthify"

	payload := strings.NewReader("{\n  \"prompt\": \"<string>\",\n  \"rephrase\": true,\n  \"model\": \"<string>\",\n  \"tone\": \"<string>\",\n  \"writingMode\": \"<string>\",\n  \"qualityMode\": \"<string>\",\n  \"outputFormat\": \"<string>\"\n}")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("api-token", "<api-token>")
	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

HttpResponse<String> response = Unirest.post("https://www.stealthgpt.ai/api/stealthify")
  .header("api-token", "<api-token>")
  .header("Content-Type", "application/json")
  .body("{\n  \"prompt\": \"<string>\",\n  \"rephrase\": true,\n  \"model\": \"<string>\",\n  \"tone\": \"<string>\",\n  \"writingMode\": \"<string>\",\n  \"qualityMode\": \"<string>\",\n  \"outputFormat\": \"<string>\"\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://www.stealthgpt.ai/api/stealthify")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["api-token"] = '<api-token>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"prompt\": \"<string>\",\n  \"rephrase\": true,\n  \"model\": \"<string>\",\n  \"tone\": \"<string>\",\n  \"writingMode\": \"<string>\",\n  \"qualityMode\": \"<string>\",\n  \"outputFormat\": \"<string>\"\n}"

response = http.request(request)
puts response.read_body

{
  "result": "<string>",
  "howLikelyToBeDetected": 123,
  "remainingCredits": 123,
  "wordsSpent": 123,
  "billingMode": "<string>",
  "meteredChargedCredits": 123
}

POST

api

stealthify

Writer & Humanizer

curl --request POST \
  --url https://www.stealthgpt.ai/api/stealthify \
  --header 'Content-Type: application/json' \
  --header 'api-token: <api-token>' \
  --data '
{
  "prompt": "<string>",
  "rephrase": true,
  "model": "<string>",
  "tone": "<string>",
  "writingMode": "<string>",
  "qualityMode": "<string>",
  "outputFormat": "<string>"
}
'

import requests

url = "https://www.stealthgpt.ai/api/stealthify"

payload = {
    "prompt": "<string>",
    "rephrase": True,
    "model": "<string>",
    "tone": "<string>",
    "writingMode": "<string>",
    "qualityMode": "<string>",
    "outputFormat": "<string>"
}
headers = {
    "api-token": "<api-token>",
    "Content-Type": "application/json"
}

response = requests.post(url, json=payload, headers=headers)

print(response.text)

const options = {
  method: 'POST',
  headers: {'api-token': '<api-token>', 'Content-Type': 'application/json'},
  body: JSON.stringify({
    prompt: '<string>',
    rephrase: true,
    model: '<string>',
    tone: '<string>',
    writingMode: '<string>',
    qualityMode: '<string>',
    outputFormat: '<string>'
  })
};

fetch('https://www.stealthgpt.ai/api/stealthify', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://www.stealthgpt.ai/api/stealthify",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => json_encode([
    'prompt' => '<string>',
    'rephrase' => true,
    'model' => '<string>',
    'tone' => '<string>',
    'writingMode' => '<string>',
    'qualityMode' => '<string>',
    'outputFormat' => '<string>'
  ]),
  CURLOPT_HTTPHEADER => [
    "Content-Type: application/json",
    "api-token: <api-token>"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://www.stealthgpt.ai/api/stealthify"

	payload := strings.NewReader("{\n  \"prompt\": \"<string>\",\n  \"rephrase\": true,\n  \"model\": \"<string>\",\n  \"tone\": \"<string>\",\n  \"writingMode\": \"<string>\",\n  \"qualityMode\": \"<string>\",\n  \"outputFormat\": \"<string>\"\n}")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("api-token", "<api-token>")
	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

HttpResponse<String> response = Unirest.post("https://www.stealthgpt.ai/api/stealthify")
  .header("api-token", "<api-token>")
  .header("Content-Type", "application/json")
  .body("{\n  \"prompt\": \"<string>\",\n  \"rephrase\": true,\n  \"model\": \"<string>\",\n  \"tone\": \"<string>\",\n  \"writingMode\": \"<string>\",\n  \"qualityMode\": \"<string>\",\n  \"outputFormat\": \"<string>\"\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://www.stealthgpt.ai/api/stealthify")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["api-token"] = '<api-token>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"prompt\": \"<string>\",\n  \"rephrase\": true,\n  \"model\": \"<string>\",\n  \"tone\": \"<string>\",\n  \"writingMode\": \"<string>\",\n  \"qualityMode\": \"<string>\",\n  \"outputFormat\": \"<string>\"\n}"

response = http.request(request)
puts response.read_body

{
  "result": "<string>",
  "howLikelyToBeDetected": 123,
  "remainingCredits": 123,
  "wordsSpent": 123,
  "billingMode": "<string>",
  "meteredChargedCredits": 123
}

The /api/stealthify endpoint is the core of the StealthGPT API, allowing you to generate new content or rephrase existing text to be undetectable by AI detection tools.

model is required. You must explicitly pass "super", "standard", or "lite". Requests that omit model return 400 Bad Request. There is no default, please pick one.

For integrations that cannot keep a request open, use the async POST /api/stealthify/runs flow. rephrase works the same way there. This synchronous endpoint remains unchanged for existing API clients.

Humanization automatically strips invisible AI text watermarks. Claude and Gemini embed a statistical pattern in their word choices, invisible to a reader, but it travels with copy and paste and can survive light editing. The humanizer rewrites at the sentence and structure level rather than swapping synonyms, which is the category of change those marks are not built to survive. Meaning stays intact; Claude, Gemini SynthID, and other invisible text watermarks do not.

Request Parameters

string

required

Your unique API authentication token. You can find this in your StealthGPT dashboard under the API Key tab.

string

required

When rephrase is false, the topic or instructions for content generation. When rephrase is true, the existing text to humanize — send only that source text, with no instruction wrappers. Maximum 3,000 words per request.

boolean

required

Set to true to rephrase the provided prompt text, or false to generate new content based on the prompt

string

required

Selects the humanizer model. Required — you must pass one of "super", "standard", or "lite". Omitting model returns 400. See Models for a full comparison.

Show Available model options

Flagship. Next-gen humanizer billed at $0.05 / 100 words. Highest bypass rate; the structural rewrite also strips invisible text watermarks such as Claude’s mark and Gemini’s SynthID.

Billed at $0.20 / 1,000 words. Previous-generation full rewrite; removes invisible text watermarks such as Claude’s mark and Gemini’s SynthID.

Fast AI-smell cleanup that keeps the text mostly unchanged. Billed at $0.20 / 1,000 words. This mode is not designed to bypass AI detectors.

Humanize / rephrase input: when rephrase is true, put only the source text in prompt. Do not add instructions such as “Humanize the following text”, “Rewrite this to sound more human”, or “Make this undetectable”. Those prefixes confuse the model and hurt output quality. Control style with API parameters (tone, model, qualityMode, etc.) instead. Instruction-style prompts are for generation (rephrase: false) only.

string

Controls the style and complexity of generated content when writingMode is essay (ignored in default mode and when rephrase is true)

Show Available tone options

default

Ideal for casual writing. Easy to read and understand, suitable for general purposes.

Mimics the style of high school level writing. May contain grammatical errors. Scores high on Flesch-Kincaid Readability.

Semi-complex style typical of college-level writing. May include minor grammatical errors. Moderate Flesch-Kincaid Readability score.

Complex, sophisticated style. No grammatical errors. Low Flesch-Kincaid Readability score, ideal for academic writing.

string

default:"default"

Controls how content is generated when rephrase is false. Has no effect when rephrase is true.

Show Available writingMode options

default

Follows the user’s prompt as written. Does not force essay structure — suitable for emails, lists, product copy, summaries, or any other format you specify.

Structures the output as an academic essay. Use with tone to set education level (Standard, HighSchool, College, PhD).

string

default:"quality"

Controls rewrite quality vs speed.

Show Available qualityMode options

Default. Runs our quality checks/repairs for better reliability and lower detection risk.

Skips quality checks/repairs and performs a single-pass rewrite. Output may have more errors and be more detectable.

string

default:"text"

Controls the formatting of the returned content.

Show Available output formats

Default format. Returns plain text output.

Returns formatted content with markdown syntax (headings, lists, bold, etc.).

Response

string

The generated or rephrased content

number

Human-likeness score from 0 to 100. Higher is better: a higher score means the content reads as more human and is less likely to be flagged as AI; a lower score means it is more likely to be detected as AI-generated. (The field name is historical — treat a higher value as the better result.)

number

Prepaid word balance remaining after this request.

number

Words charged for this request.

string

Whether the request was billed from prepaid words (prepaid) or pay-as-you-go metered billing (payg).

number

If billed via pay-as-you-go, words added to metered usage for this request (0 when billed from prepaid).

Example Request

curl --location 'https://www.stealthgpt.ai/api/stealthify' \
    --header 'api-token: YOUR_API_TOKEN' \
    --header 'Content-Type: application/json' \
    --data '{
        "prompt": "Explain the benefits of renewable energy",
        "rephrase": false,
        "writingMode": "essay",
        "tone": "College",
        "qualityMode": "quality",
        "model": "super",
        "outputFormat": "markdown"
    }'

import requests

response = requests.post(
    'https://www.stealthgpt.ai/api/stealthify',
    headers={
        'api-token': 'YOUR_API_TOKEN',
        'Content-Type': 'application/json'
    },
    json={
        'prompt': 'Explain the benefits of renewable energy',
        'rephrase': False,
        'writingMode': 'essay',
        'tone': 'College',
        'qualityMode': 'quality',
        'model': 'super',
        'outputFormat': 'markdown'
    }
)

print(response.json())

const axios = require('axios');

axios.post('https://www.stealthgpt.ai/api/stealthify', {
    prompt: 'Explain the benefits of renewable energy',
    rephrase: false,
    writingMode: 'essay',
    tone: 'College',
    qualityMode: 'quality',
    model: 'super',
    outputFormat: 'markdown'
}, {
    headers: {
        'api-token': 'YOUR_API_TOKEN',
        'Content-Type': 'application/json'
    }
}).then(response => {
    console.log(response.data);
});

Super is billed at $0.05 / 100 words (vs $0.20 / 1,000 words for standard and lite). Both rates apply to input words plus output words.

Example Response

{
  "result": "Renewable energy offers several significant advantages in our modern world. Students and researchers point to multiple benefits like reduced carbon emissions, which helps fight climate change. These energy sources, including solar and wind power, represent inexhaustible resources unlike finite fossil fuels. Many communities find economic advantages through job creation in the growing renewable sector. Additionally, these technologies typically require less maintenance after installation and reduce dependency on foreign energy imports. Advancements continue making these options more cost-competitive, with prices dropping significantly over recent years. While challenges exist in implementation, the long-term benefits to environmental health, economic stability, and energy independence make renewable energy sources increasingly attractive options for our global energy needs.",
  "howLikelyToBeDetected": 92,
  "wordsSpent": 260,
  "remainingCredits": 985000,
  "billingMode": "prepaid",
  "meteredChargedCredits": 0
}

Usage Notes

For optimal performance, we recommend keeping responses under 2,000 characters
When rephrase is true, send only the source text in prompt — no “humanize / rewrite / make undetectable” wrappers
When rephrase is false, the quality and relevance of generated content depends on the phrasing of your prompts
Humanization automatically strips invisible AI text watermarks (Claude, Gemini SynthID, and similar marks) as part of the sentence-level rewrite, no extra parameter
For more advanced usage techniques, see our Advanced Usage Guide

Getting Started

Endpoints

Stealth Agent

Integrations

Resources

Writer & Humanizer

Request Parameters

Response

Example Request

Example Response

Usage Notes

​Request Parameters

​Response

​Example Request

​Example Response

​Usage Notes

Request Parameters

Response

Example Request

Example Response

Usage Notes