Build a WhatsApp Bot in Node.js

Install and authenticate

Install

npm install express (fetch is built in from Node 18)

Token

process.env.WAPITO_TOKEN

Webhook receiver

Express 5 npm install express

Every call is one HTTPS request with a Bearer token, so there is no SDK to wait for and nothing to keep in step with a release. The REST API reference documents every endpoint with a snippet in this language.

19 tutorials

Gotchas

• fetch never rejects on a 4xx or 5xx. Check response.ok yourself; an await fetch(...) that "worked" can still be a 402 plan_required with a JSON error body.
• Do not let express.json() run before your webhook route. Signature verification needs the exact raw bytes, so mount express.raw({ type: "application/json" }) on the webhook path and parse the JSON yourself afterwards.
• Node 18+ has global fetch, but node-fetch v2, undici and axios all disagree about how they surface non-2xx responses. Pick one client per project or your error handling will be inconsistent.
• Promise.all over a list of recipients defeats the send queue: the API will serialise them anyway and return 429 send_rate_limited for the overflow. Send sequentially with await, or use a queue with concurrency 1 per channel.
• Large numbers in JSON.parse lose precision. Treat every WhatsApp id, group id and timestamp that arrives as a string as a string - never Number() it.

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