Ethereum explorer APIs: free tiers, keys and real limits

An Ethereum blockchain explorer API gives your code the same indexed data you see on an explorer website: an address’s full transaction history, token transfers, verified contract ABIs, token holders and prices. That is exactly the data a raw Ethereum node does not give you. The catch is that every provider meters it differently, and several changed their free tiers in 2025 and 2026. This guide compares the options we tested in September 2026, shows two short code examples and explains the one mistake that ruins most hobby projects: an API key embedded in frontend code.

Explorer API or JSON-RPC: what is the difference?

Every Ethereum node speaks JSON-RPC. It answers questions about current state and individual objects: the balance of an address, the receipt of a known transaction hash, the contents of block 26,000,000, the result of calling a contract function. What it cannot do is answer “show me every transaction this address ever sent” or “who holds this token”, because nodes do not keep those indexes. An explorer runs an indexer on top of nodes, builds those tables and exposes them through an explorer API.

The practical rule: if you already know the hash or only need current state, JSON-RPC is enough and often keyless. If you need history, token lists, holders, decoded logs or verified source code, you need an explorer API or an indexing service. Many apps use both, and so does our own tool.

Etherscan API V2: the default, now with tighter free limits

Etherscan’s API V2 is the one most tutorials use. One key works across roughly 60 to 70 EVM chains, selected with a chainid parameter, for example api.etherscan.io/v2/api?chainid=1&module=account&action=balance&address=0x…&apikey=YOUR_KEY. The modules cover accounts, contracts (source and ABI), transactions, blocks, logs, tokens, gas and stats. The old V1 endpoints were switched off on 15 August 2025; when we called one, it replied with a pointer to the V2 migration guide.

The free plan allows 3 calls per second and 100,000 calls per day, requires a key and asks for attribution. Three changes matter in 2026. On 22 November 2025 Base, BNB Chain, OP Mainnet, Avalanche and Gnosis moved to paid plans, which start with a Lite tier at $49 a month; Ethereum mainnet stays free. Since 1 July 2026 list endpoints such as txlist, tokentx and getLogs return at most 1,000 records per request on the free tier instead of 10,000, so pagination code written for the old limit silently misses data. And internal transactions by block range moved behind the paid Pro plans. Verified source code and ABI endpoints stay available on every plan. Our Etherscan review covers the website side.

Blockscout REST API v2 and the Etherscan-compatible API

Blockscout runs explorers for more than 100 chains, with Ethereum at eth.blockscout.com. Each instance exposes two interfaces. The REST API v2 under /api/v2/ is the modern one, with clean JSON for transactions, addresses, tokens, token balances, logs, internal transactions, blobs and EIP-7702 authorisations. The legacy RPC API under /api?module=…&action=… mirrors Etherscan’s parameters, so a lot of existing code works after changing the base URL. On the Ethereum instance both currently work without a key: a keyless balance call returned vitalik.eth’s 6.7179 ETH instantly.

const hash = '0x2f1c5c2b44f771e942a8506148e256f94f1a464babc938ae0690c6e34cd79190';
const res = await fetch(`https://eth.blockscout.com/api/v2/transactions/${hash}`);
const tx = await res.json();
console.log(tx.block_number, tx.result, tx.fee.value);
// 4634748 'success' '12683176000000000'  (the USDT deployment, Nov 2017)

Keyless requests are rate-limited per IP, and responses include x-ratelimit-limit and x-ratelimit-remaining headers so you can back off politely. Two caveats. Blockscout’s documentation now steers developers to a keyed multichain PRO API at api.blockscout.com; the free key gives 5 requests per second and 100,000 credits a day, which at the default 20 credits per call is roughly 5,000 requests. The docs also warn that scripted server-side traffic to public instances can hit a bot-protection challenge. Our advice: use the public instance for browser apps and prototypes, and a free PRO key for backend jobs. Note that Blockscout’s current releases are source-available under the Blockscout Software License (earlier versions were GPL-3.0). Details are in our Blockscout review.

Routescan, Blockchair and Ethplorer

Routescan offers an Etherscan-compatible API for 70+ chains at URLs such as api.routescan.io/v2/network/mainnet/evm/1/etherscan/api. Without a key you get 2 requests per second and 10,000 calls a day; a free registered key raises that to 5 per second and 100,000 a day. For code that already speaks Etherscan’s dialect, it is the easiest keyless fallback.

Blockchair is the choice for multi-chain or analytical queries. Its tables accept SQL-like filters, sorting and aggregation, and the same call pattern works on Bitcoin and Ethereum. The free allowance is small: about 1,440 requests a day for personal or non-commercial use with a hard cap of 30 per minute, and commercial use needs a paid key. Our test IP was temporarily blacklisted after a handful of calls, so do not build on the free tier. More in our Blockchair review.

Ethplorer is token-first. One getAddressInfo call returns every ERC-20 balance of an address with USD prices, which would take several calls elsewhere. The shared freekey is capped at 2 requests per second and 1,000 per day; a free personal key allows 10 per second. See the Ethplorer review for the full limits.

Specialist APIs: beaconcha.in and Blobscan

Consensus-layer data (validators, attestations, rewards, withdrawals) does not live in execution-layer explorers. beaconcha.in by Bitfly is the usual source, and its API now requires a key on every endpoint; the free option is a 30-day trial with 1,000 requests at one per second, after which paid plans start at about €59 a month billed annually. For light use, a beacon node’s own REST API may be cheaper. Our beacon chain explorer guide covers the alternatives.

Blobscan indexes EIP-4844 blobs, the data that rollups post to Ethereum since March 2024. Its open-source REST API at api.blobscan.com answers without a key, for example /blobs?ps=1 for the latest blob with its versioned hash, commitment and block. It is the fastest way to check whether a rollup batch landed; background in our blob explorer guide.

Public JSON-RPC endpoints and when to pay for a node

For state reads you often need no explorer at all. These keyless mainnet endpoints answered our requests with CORS enabled in September 2026: ethereum-rpc.publicnode.com, eth.drpc.org, 1rpc.io/eth and rpc.flashbots.net. Flashbots’ endpoint is mainly built for sending transactions privately, away from the public mempool, so treat it as a read fallback. Some old favourites are gone: Ankr now requires a key and Cloudflare’s gateway no longer serves requests.

curl -s https://ethereum-rpc.publicnode.com \
  -H 'content-type: application/json' \
  -d '{"jsonrpc":"2.0","id":1,"method":"eth_getBalance",
       "params":["0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045","latest"]}'
# {"jsonrpc":"2.0","id":1,"result":"0x5d3abe2cfc589d15"}  = 6.7179 ETH

Public endpoints are shared, unmetered for you and come with no guarantees. They may rate-limit you, return slightly stale data or drop eth_getLogs queries over large block ranges. Move to a node provider such as Alchemy, Infura or QuickNode when you need an uptime commitment, archive state at old blocks, debug_ or trace_ methods, WebSocket subscriptions for new blocks and pending transactions, or enhanced methods for token balances and transfer history. All three have free tiers measured in credits or compute units, so compare the quotas on their pricing pages. If you would rather run the stack yourself, our guide to the open-source Ethereum explorer options shows how to put a local explorer on your own node.

CORS and why keys never belong in frontend JavaScript

Developers often assume CORS is what stops them calling an explorer from the browser. It usually is not. We checked the response headers: Etherscan, Blockscout, Routescan, Ethplorer, Blockchair and Blobscan all send Access-Control-Allow-Origin: *, and the public RPC endpoints above allow cross-origin calls too. The browser will happily make the request.

The real problem is the key. Anything in your JavaScript bundle is public: one look at the network tab reveals it. A copied Etherscan key can exhaust your 100,000 daily calls in minutes, trigger rate-limit bans and, because the key is tied to your account, make you responsible for someone else’s traffic. Blockchair’s own documentation tells developers to put a proxy in front of the API for exactly this reason.

There are three clean patterns. Use keyless endpoints directly from the browser (Blockscout’s public instance, public RPC, Blobscan). Put keyed calls behind a proxy, such as a small serverless function that adds the key server-side, caches responses and enforces its own rate limit. Or use a node provider that supports domain allowlisting on browser keys. Our live Ethereum explorer takes the first route: it is a static site with no server, and your browser talks straight to Blockscout’s API v2 with public JSON-RPC nodes as fallback. No key, nothing to leak.

Ethereum block explorer APIs compared

The table summarises free access as we verified it on 24 September 2026. Limits change often, so recheck the provider’s documentation before you design around a number.

Our picks

For a frontend-only app, start with Blockscout’s public API v2 plus a public RPC fallback. For a backend script on Ethereum mainnet, Etherscan’s free key is fine as long as you paginate in 1,000-record pages; keep Routescan as a drop-in backup. For portfolio or token dashboards, Ethplorer saves calls. For production, pay for a node provider or a paid explorer plan: free tiers are for building, not for serving thousands of users. If you are still choosing an explorer for manual work, our ranking of the best Ethereum explorers and the list of Etherscan alternatives cover the websites behind these APIs.