Webhooks

Spectrum Webhooks push real-time blockchain events to your server. Instead of polling the chain, you register the addresses you care about and Spectrum delivers a signed HTTPS POST to a URL you own whenever those addresses appear in on-chain activity.

How it works

1. Create a webhook. Choose a chain, a destination URL, and the addresses you want to watch. Optionally narrow delivery to specific token contracts or activity categories.
2. Spectrum watches the chain in real time. As each block is produced, Spectrum decodes its activity and checks whether any watched address is the sender (from) or receiver (to).
3. Matching events are delivered. Every event from that block that matches your webhook is bundled into a single HTTPS POST, signed with your webhook’s key. Block-level fields sit on the envelope; each matched event is one entry in event.activity[].
4. Your server verifies and processes. Check the X-Spectrum-Signature header, then handle the events (including any reorg rollbacks, flagged with event.removed: true).

On-chain activity  ──►  Spectrum listener  ──►  signed HTTPS POST  ──►  your server
   (watched address)      (real-time)           (X-Spectrum-Signature)

Supported webhook type

Spectrum currently offers a single webhook type, Address Activity (ADDRESS_ACTIVITY). It watches addresses on Ethereum and Polygon and delivers the native, token, and NFT transfers they take part in. The type field is what selects the webhook type, so new types can be added over time without changing existing webhooks.

Activity categories

Every delivered event carries a category describing the kind of transfer. A webhook receives all categories by default, or you can pick which ones you want when you create the webhook.

See Activity Categories for the exact fields each category delivers.

Why use webhooks

• Real-time. Events arrive as blocks are produced, no polling loops, no eth_getLogs cron jobs.
• Decoded. Native transfers, ERC-20, ERC-721 and ERC-1155 activity arrive already decoded, with token symbols and human-readable amounts where available.
• Reliable. Deliveries are retried with backoff, dead-lettered if your endpoint stays down, and are at-least-once, you never silently miss an event.
• Secure. Every delivery is signed with an HMAC key so you can verify it came from Spectrum.
• Reorg-aware. If a delivered block is later orphaned, Spectrum sends a follow-up so you can roll back derived state.

Managing webhooks

You create and manage webhooks from the Webhooks section of the Spectrum dashboard. A single webhook can watch many addresses and, optionally, filter down to specific token contracts.

Next steps

• Creating a Webhook: register your first webhook, set filters and fields, and save its signing key.
• Activity Categories: what Address Activity captures and what each category delivers.
• Delivery & Retries: the payload, headers, retry policy, idempotency, reorgs, and monitoring.
• Signing & Verification: verify signatures and rotate keys.