# Response compression

> Prefer zstd responses, use gzip for compatibility, and prepare for uncompressed response retirement.

Canonical page: https://rpc.aurpay.net/docs/response-compression

Prefer **zstd** for JSON-RPC responses and HTTP API responses on TRON, with **gzip** as a compatibility fallback. Uncompressed (`identity`) responses remain supported for now, but are planned for removal. New integrations should support compression.

## Request compressed responses

Enable your client's zstd decoder before advertising support; some clients require an optional dependency or build feature. For clients supporting both formats, use:

```http
Accept-Encoding: zstd, gzip;q=0.8
```

Higher `q` values take priority; equal values prefer zstd, then gzip. `q=0` rejects an encoding, and explicit entries override `*`. See [negotiation errors](https://rpc.aurpay.net/docs/errors.md#response-negotiation-errors) if all available encodings are rejected.

With curl, `--compressed` advertises the encodings supported by your installed build and automatically decodes the response:

```bash
curl --compressed "$RPC_URL" \
  -H "Authorization: Bearer $APP_API_KEY" \
  -H 'Content-Type: application/json' \
  --data '{"jsonrpc":"2.0","id":1,"method":"eth_blockNumber","params":[]}'
```

Set `RPC_URL` to your Gateway Access Point without an API Key in its path, and `APP_API_KEY` to your App API Key. See [Authentication](https://rpc.aurpay.net/docs/authentication.md).

## Decode the response

Follow the actual `Content-Encoding`, including when a proxy changes it. HTTP clients commonly decode supported responses automatically; do not decompress twice. For raw HTTP bytes, decode before parsing JSON. The decoded body is unchanged.

Read streamed responses to completion without requiring `Content-Length`. Individual chunks are not complete JSON documents. Negotiable responses include `Vary: Accept-Encoding`.

For now, absent or empty `Accept-Encoding` leaves responses uncompressed. Small responses also normally remain uncompressed unless `identity` is forbidden. Without `Content-Encoding`, read the body directly.

Known-empty responses bypass compression. SSE, partial responses, `no-transform` responses and existing encodings are passed through only when their encoding is acceptable; otherwise, see [negotiation errors](https://rpc.aurpay.net/docs/errors.md#response-negotiation-errors).

## Related

- [JSON-RPC](https://rpc.aurpay.net/docs/json-rpc.md)
- [TRON](https://rpc.aurpay.net/docs/chains/tron.md)
- [Errors and recovery](https://rpc.aurpay.net/docs/errors.md)