How to upload files through Telegram bot API using Node.js

[elizabeths]

I’m trying to upload a file to a Telegram chat using the bot API in JavaScript but getting an error message that says “Bad Request: there is no document in the request”. Here’s my current code:

const filePath = path.resolve(__dirname, "sample.pdf");
const fileData = fs.readFileSync(filePath);
const buffer = Buffer.from(fileData, "binary");
const form = new FormData();
form.append("chat_id", chatId);
form.append("document", buffer, {
  filename: "sample.pdf",
});
form.append("caption", "Here is your requested file");

const apiCall = await fetch(
  `https://api.telegram.org/bot${TOKEN}/sendDocument`,
  {
    method: "POST",
    headers: {
      accept: "application/json",
    },
    body: form,
  }
);

const result = await apiCall.json();
console.log(result);

I want to be able to send different types of files like PDFs, Word documents, or compressed archives from my Node.js server to users in Telegram. What am I doing wrong with the file attachment?

[Grace_31Dance]

Your file reading approach is the problem. fs.readFileSync() already returns a Buffer when you don’t specify encoding, so wrapping it with Buffer.from(fileData, "binary") is pointless and probably corrupting your data.

Try this instead:

const filePath = path.resolve(__dirname, "sample.pdf");
const fileStream = fs.createReadStream(filePath);
const form = new FormData();
form.append("chat_id", chatId);
form.append("document", fileStream, "sample.pdf");
form.append("caption", "Here is your requested file");

createReadStream works better for bigger files and dodges encoding headaches. Double-check your file path exists too. I’ve used this with PDFs, ZIPs, you name it - works every time.

[DancingFox]

The issue lies in how you’re managing the file data. Using fs.readFileSync() without any encoding returns a Buffer object directly. Converting it again with Buffer.from(fileData, "binary") results in a corrupted buffer that Telegram cannot process. I’ve encountered this exact issue before and resolved it like this:

const filePath = path.resolve(__dirname, "sample.pdf");
const fileBuffer = fs.readFileSync(filePath);
const form = new FormData();
form.append("chat_id", chatId);
form.append("document", fileBuffer, {
  filename: "sample.pdf",
  contentType: "application/pdf"
});
form.append("caption", "Here is your requested file");

Additionally, eliminate the accept header from your fetch request. The form-data library handles the content type on its own, and adding extra headers can interfere with the multipart boundary. This method works well for PDFs, Word documents, archives, and more.

[alexr1990]

sounds like a form-data setup probs. install the form-data package using npm install form-data. don’t set content-type headers yourself - let FormData manage it. i faced the same issue & removing the accept header worked for me.