ProvenPin Install

file-type buffer detection: working versions (tested 2026-10-16)

Detect PNG, PDF, ZIP and GIF from small in-memory magic byte buffers with file-type, asserting ext and mime, and undefined for plain text.

passed5 passed · 0 failed2026-10-16 19:54 UTC
Status
passed
Last passed
2026-10-16 19:54 UTC
Tests
5 / 5
Language
TypeScript
Runtime
node v22.23.3
pinned versions3
file-type@22.2.0@types/node@26.6.5tsx@4.23.15
run it
npm install --no-audit --no-fund --ignore-scripts=false
npm test
test environment
node v22.23.3
linux 6.17.0-1022-azure
x64
runner: github-actions 38958328921

The code

Exactly the files that passed. Your agent can pull them with get_recipe("file-type-buffer-detect") (install), or see them on GitHub.

package.json
{
  "name": "file-type-buffer-detect",
  "private": true,
  "type": "module",
  "scripts": {
    "test": "node --import tsx --test test/*.test.ts"
  },
  "dependencies": {
    "file-type": "22.2.0"
  },
  "devDependencies": {
    "@types/node": "26.6.5",
    "tsx": "4.23.15"
  }
}
src/detect.ts
import { fileTypeFromBuffer } from "file-type";

export type Detected = {
  ext: string;
  mime: string;
};

export async function detect(bytes: Uint8Array): Promise<Detected | undefined> {
  const result = await fileTypeFromBuffer(bytes);
  if (!result) {
    return undefined;
  }
  return { ext: result.ext, mime: result.mime };
}
test/detect.test.ts
import { test } from "node:test";
import assert from "node:assert/strict";
import { detect } from "../src/detect.ts";

const bytes = (values: number[]): Uint8Array => Uint8Array.from(values);

const PNG = bytes([
  0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a,
  0x00, 0x00, 0x00, 0x0d, 0x49, 0x48, 0x44, 0x52,
]);

const PDF = bytes([
  0x25, 0x50, 0x44, 0x46, 0x2d, 0x31, 0x2e, 0x37,
  0x0a, 0x25, 0xe2, 0xe3, 0xcf, 0xd3, 0x0a, 0x0a,
]);

const ZIP = bytes([
  0x50, 0x4b, 0x03, 0x04, 0x14, 0x00, 0x00, 0x00,
  0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
]);

const GIF = bytes([
  0x47, 0x49, 0x46, 0x38, 0x39, 0x61, 0x64, 0x00,
  0x64, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
]);

test("detects png from magic bytes", async () => {
  assert.deepEqual(await detect(PNG), { ext: "png", mime: "image/png" });
});

test("detects pdf from magic bytes", async () => {
  assert.deepEqual(await detect(PDF), { ext: "pdf", mime: "application/pdf" });
});

test("detects zip from magic bytes", async () => {
  assert.deepEqual(await detect(ZIP), { ext: "zip", mime: "application/zip" });
});

test("detects gif from magic bytes", async () => {
  assert.deepEqual(await detect(GIF), { ext: "gif", mime: "image/gif" });
});

test("returns undefined for plain text", async () => {
  const text = new TextEncoder().encode("just some plain text, not a binary format");
  assert.equal(await detect(text), undefined);
});

Connect to ProvenPin

Add the free MCP server so your agent can pull this recipe and others like it. Same setup as the docs.

terminal
claude mcp add --transport http provenpin https://mcp.provenpin.com/mcp

Any other MCP client: Streamable HTTP at https://mcp.provenpin.com/mcp. No API key, no signup.