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Quickstart

Website screenshots in Go

One HTTPS request, net/http, and no browser of your own to keep running.

Renderwolf is a plain HTTPS API, so Go needs no SDK - net/http is enough. A successful render returns the image bytes directly, with no JSON envelope and no base64, so you write the response straight to a file.

Get a key

Create one in the portal. It is shown once and stored hashed, so put it in an environment variable rather than in the file - the samples below read it from one.

Take a screenshot

package main

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"os"
)

func main() {
	body, _ := json.Marshal(map[string]any{
		"url":   "https://example.com",
		"width": 1280,
	})

	req, _ := http.NewRequest("POST",
		"https://api.ironfang.uk/renderwolf/v1/screenshot",
		bytes.NewReader(body))
	req.Header.Set("Authorization", "Bearer "+key)
	req.Header.Set("Content-Type", "application/json")

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		panic(err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		var e struct {
			Error struct{ Code, Message string } `json:"error"`
		}
		json.NewDecoder(resp.Body).Decode(&e)
		panic(fmt.Sprintf("%s: %s", e.Error.Code, e.Error.Message))
	}

	out, _ := os.Create("shot.png")
	defer out.Close()
	io.Copy(out, resp.Body)
}

Handling errors

Success is binary; every error is JSON, shaped as {"error": {"code", "message"}}. A missing or unknown key is 401 invalid_api_key, and a key without the renderwolf:render scope is 403.

// io.Copy streams the response straight to disk rather than
// buffering it. A full-page screenshot of a long page can be several
// megabytes, and there is no reason for it to pass through memory.

PDFs and templates

The same call shape works for /v1/pdf, and for templated images at /v1/image/{id}. Only the path and the body change.

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