OG Image API
Generate Open Graph images, banners, and social cards from HTML templates with {{variables}} — design once, render thousands.
POST /v1/image → Binary image (image/png, image/jpeg, or image/webp)
Example
curl -X POST https://rasterkit.com/v1/image \
-H "x-api-key: $RASTERKIT_API_KEY" \
-H "content-type: application/json" \
-d '{"template_id": "tpl_your_template", "variables": {"title": "Hello World", "author": "Paul"}}' \
-o og-image.png import { writeFile } from 'node:fs/promises'
const res = await fetch('https://rasterkit.com/v1/image', {
method: 'POST',
headers: {
'x-api-key': process.env.RASTERKIT_API_KEY,
'content-type': 'application/json',
},
body: JSON.stringify({"template_id": "tpl_your_template", "variables": {"title": "Hello World", "author": "Paul"}}),
})
if (!res.ok) throw new Error(`Render failed: ${res.status} ${await res.text()}`)
await writeFile('og-image.png', Buffer.from(await res.arrayBuffer()))
console.log('Saved og-image.png') import os
import requests
res = requests.post(
"https://rasterkit.com/v1/image",
headers={"x-api-key": os.environ["RASTERKIT_API_KEY"]},
json={"template_id": "tpl_your_template", "variables": {"title": "Hello World", "author": "Paul"}},
timeout=60,
)
res.raise_for_status()
with open("og-image.png", "wb") as f:
f.write(res.content)
print("Saved og-image.png") <?php
$ch = curl_init('https://rasterkit.com/v1/image');
curl_setopt_array($ch, [
CURLOPT_POST => true,
CURLOPT_RETURNTRANSFER => true,
CURLOPT_TIMEOUT => 60,
CURLOPT_HTTPHEADER => [
'x-api-key: ' . getenv('RASTERKIT_API_KEY'),
'content-type: application/json',
],
CURLOPT_POSTFIELDS => '{"template_id": "tpl_your_template", "variables": {"title": "Hello World", "author": "Paul"}}',
]);
$body = curl_exec($ch);
$status = curl_getinfo($ch, CURLINFO_RESPONSE_CODE);
curl_close($ch);
if ($status !== 200) {
throw new RuntimeException("Render failed: $status $body");
}
file_put_contents('og-image.png', $body);
echo "Saved og-image.png\n"; require "net/http"
require "json"
uri = URI("https://rasterkit.com/v1/image")
req = Net::HTTP::Post.new(uri)
req["x-api-key"] = ENV.fetch("RASTERKIT_API_KEY")
req["content-type"] = "application/json"
req.body = '{"template_id": "tpl_your_template", "variables": {"title": "Hello World", "author": "Paul"}}'
res = Net::HTTP.start(uri.hostname, uri.port, use_ssl: true, read_timeout: 60) { |http| http.request(req) }
raise "Render failed: #{res.code} #{res.body}" unless res.code == "200"
File.binwrite("og-image.png", res.body)
puts "Saved og-image.png" package main
import (
"bytes"
"fmt"
"io"
"net/http"
"os"
"time"
)
func main() {
body := []byte(`{"template_id": "tpl_your_template", "variables": {"title": "Hello World", "author": "Paul"}}`)
req, _ := http.NewRequest("POST", "https://rasterkit.com/v1/image", bytes.NewReader(body))
req.Header.Set("x-api-key", os.Getenv("RASTERKIT_API_KEY"))
req.Header.Set("content-type", "application/json")
client := &http.Client{Timeout: 60 * time.Second}
res, err := client.Do(req)
if err != nil {
panic(err)
}
defer res.Body.Close()
data, _ := io.ReadAll(res.Body)
if res.StatusCode != 200 {
panic(fmt.Sprintf("render failed: %d %s", res.StatusCode, data))
}
os.WriteFile("og-image.png", data, 0644)
fmt.Println("Saved og-image.png")
} import java.net.URI;
import java.net.http.*;
import java.nio.file.*;
import java.time.Duration;
public class Render {
public static void main(String[] args) throws Exception {
String body = """
{"template_id": "tpl_your_template", "variables": {"title": "Hello World", "author": "Paul"}}""";
HttpRequest request = HttpRequest.newBuilder()
.uri(URI.create("https://rasterkit.com/v1/image"))
.timeout(Duration.ofSeconds(60))
.header("x-api-key", System.getenv("RASTERKIT_API_KEY"))
.header("content-type", "application/json")
.POST(HttpRequest.BodyPublishers.ofString(body))
.build();
HttpResponse<byte[]> res = HttpClient.newHttpClient()
.send(request, HttpResponse.BodyHandlers.ofByteArray());
if (res.statusCode() != 200) {
throw new RuntimeException("Render failed: " + res.statusCode() + " " + new String(res.body()));
}
Files.write(Path.of("og-image.png"), res.body());
System.out.println("Saved og-image.png");
}
} using System.Text;
var client = new HttpClient { Timeout = TimeSpan.FromSeconds(60) };
client.DefaultRequestHeaders.Add("x-api-key",
Environment.GetEnvironmentVariable("RASTERKIT_API_KEY"));
var body = new StringContent(
"""{"template_id": "tpl_your_template", "variables": {"title": "Hello World", "author": "Paul"}}""",
Encoding.UTF8, "application/json");
var res = await client.PostAsync("https://rasterkit.com/v1/image", body);
var bytes = await res.Content.ReadAsByteArrayAsync();
if (!res.IsSuccessStatusCode)
throw new Exception($"Render failed: {(int)res.StatusCode} {Encoding.UTF8.GetString(bytes)}");
await File.WriteAllBytesAsync("og-image.png", bytes);
Console.WriteLine("Saved og-image.png"); Parameters
Send as a JSON body. Exactly the same fields work as query parameters on the signed GET variant.
| Parameter | Type | Default | Description |
|---|---|---|---|
template_id | string | — | A stored template (create via dashboard or POST /v1/templates). Exactly one of template_id or template_html. |
template_html | string ≤500KB | — | Inline HTML/CSS template with {{handlebars}} variables. |
variables | object | {} | Values substituted into the template. HTML-escaped by default; {{{var}}} opts out. |
width | int 64–4096 | 1200 | Output width (1200×630 = OG standard). |
height | int 64–4096 | 630 | Output height. |
device_scale_factor | number 1–3 | 1 | Retina scaling. |
format | png | jpeg | webp | png | Output encoding. |
quality | int 1–100 | 80 | jpeg/webp quality. |
timeout_ms | int 1000–60000 | 30000 | Render time cap. |
cache_ttl | int 0–604800 (s) | 0 | Cache identical renders. |
async | bool | false | Return 202 + job id immediately instead of waiting. |
webhook_url | url | — | POSTed (signed) when an async job finishes. |
Responses
- 200 — the binary result. Headers include
x-rasterkit-cache: HIT|MISSandx-rasterkit-render-ms. - 202 — when
async: true; body is{ "id", "status", "status_url" }. See async jobs. - 4xx/5xx — JSON envelope
{ "error": { "code", "message", "docs" } }. Full catalog: errors.
Inline templates
For one-offs or previews, pass template_html directly instead of template_id:
{
"template_html": "<div style='width:1200px;height:630px;display:flex;align-items:center;justify-content:center;background:#0b0d12;color:#fff'><h1 style='font-size:64px'>{{title}}</h1></div>",
"variables": { "title": "Hello World" }
} For production, store templates and reference them by id — smaller requests and central editing.
Escaping
{{variable}} values are HTML-escaped (safe for user-generated titles). {{{variable}}} injects raw HTML — only for trusted content. Helpers available: uppercase, lowercase, truncate.