# Coverage and limits

Some data is not available on every chain: depending on the chain, a call can answer `API409` or `API502`, or return `null`. This page says what, and why.

## What works where

| Capability | BTC | LTC | BCH | DASH | ETH | TRON |
| --- | --- | --- | --- | --- | --- | --- |
| Chains, live heads, blocks, transactions, status | yes | yes | yes | yes | node syncing | history from 2026-09-08 |
| Address balance | `null` until watched and active | `null` until watched and active | `null` until watched and active | exact | exact | exact |
| Address transactions | from the watch time | from the watch time | from the watch time | yes | as the explorer index lands | as the explorer index lands |
| UTXOs | watch first | watch first | watch first | yes | n/a | n/a |
| Build, estimate, assemble, broadcast, decode | yes | yes | yes | yes | node syncing | yes |
| Nonce / resources | n/a | n/a | n/a | n/a | `address/nonce` | `address/resources` |
| Mempool | yes (sample) | yes (sample) | yes (sample) | yes (sample) | `API409` while no pending view | yes (up to 50) |
| Webhooks and WebSocket | yes | yes | yes | yes | node syncing | yes |

The authoritative, live version of the chain rows is `features` in [Chains](https://docs.rarebl.com/api/stats/chains).

## The reasons, and why

- **The Ethereum node is syncing.** The Ethereum node (Erigon) is still indexing, so `tx_index_pending` (`API409`) or `API502` can come from any ETH call, including build, nonce, gas and broadcast. While it syncs, the chain shows `lagging` with a `null` tip.
- **`before_history_start`: TRON history starts on 2026-09-08.** The TRON node holds blocks from that date. A block height below it answers `API409`, and `historyFrom` in [Chains](https://docs.rarebl.com/api/stats/chains) shows the date.
- **`history_unavailable`: the history index is in progress.** [Address transactions](https://docs.rarebl.com/api/address/transactions) works on DASH. On BTC, LTC and BCH it covers an address **from the time it was watched** (not its earlier history); ETH and TRON follow as the explorer index lands. Until then it answers `API409`.
- **`not_watched`: BTC, LTC and BCH addresses need a watch** for UTXOs, exact balances and activity. A new watch is `pending` while a UTXO-set bootstrap runs, then `active`. **How long the bootstrap takes depends on the deployment and the chain:** poll [Watch addresses](https://docs.rarebl.com/api/address/watch) or [Address UTXOs](https://docs.rarebl.com/api/address/utxos) until it is active.
- **`no_mempool_view`:** [Mempool](https://docs.rarebl.com/api/tx/mempool) answers this where the node has no pending transactions to show (ETH today).

## Other limits

- **Rate limits** are per IP and per rate class. Broadcast and the other write calls are the tightest: 6 per minute, burst 3, 300 per day. See [Rate limits](https://docs.rarebl.com/rate-limits).
- **Hosted signing** needs the header `X-Rarebl-Accept-Risk: hosted-signing`, and Try It is disabled for it on this site so a private key is never typed into a web page: [Hosted signing](https://docs.rarebl.com/guides/hosted-signing).
- **Webhook deliveries** come from `167.71.28.63` ([Webhooks](https://docs.rarebl.com/guides/webhooks)). Always verify the signature as well.
- **Watches** expire after 90 days without a query or webhook. Hooks: at most 100 active subscriptions per IP.
- **The stream:** 3 connections per IP, 200 channel subscriptions each.
- **Market data** is reference data from public feeds, not Rarebl trading rates.
- **Replacing a pending ETH or TRON transaction** is not covered in v2.
- Token endpoints return **known tokens** only; `holders` and `transfers` are `null` until the index exists. On TRON, TRC-10 assets are listed with null symbols.
- On Litecoin, MWEB amounts are hidden: `fee` is `null` and unresolved input values are `null`.
- Litecoin and Bitcoin Cash resolve input addresses and values on [Transaction](https://docs.rarebl.com/api/tx/get) only, for at most 50 inputs. Output `spent` flags are looked up for at most 50 outputs.
- Mempool results on UTXO chains are a **sample**; `count` is the real size.
- `X-API-KEY` is reserved: there are no keyed plans or billing.
- Not part of the Open API today: contract and logs endpoints, an RPC proxy and usage reporting.

These limits change as the index and the Ethereum node progress. The [Changelog](https://docs.rarebl.com/changelog) records each change.