Quick answer:<\/strong> An API is the overall agreement that lets two programs exchange data. RPC (Remote Procedure Call) is a style of API organized around calling remote functions, and JSON-RPC is the plain-text version that essentially every blockchain speaks. So when someone says “Web3 API” or “blockchain API,” there’s almost always a JSON-RPC API doing the work underneath.<\/p>\n<\/blockquote>\n\n\n\n The plan from here: we start with what an API and an RPC actually are, sit REST next to RPC, then take on gRPC \u2014 the version that throws a lot of backend developers. After that it’s on-chain, and why JSON-RPC ended up the default across Web3.<\/p>\n\n\n Start with the wider term, since RPC lives inside it. An API \u2014 application programming interface \u2014 is a set of rules for how one program asks another for something. MDN<\/a> describes it as an interface that hides complexity behind a stable set of operations. The restaurant metaphor is worn out, but it works: you order off a menu, the kitchen does the part you never see, a plate comes back. That same pattern runs most of the software you touch, from the weather widget on your phone to a blockchain endpoint handing back a wallet balance.<\/p>\n\n\n APIs don’t all share one design. They solve the same problem \u2014 structured communication between programs \u2014 but each makes different bets on speed, structure, and how long it takes to learn. Four come up often:<\/p>\n\n\n\n RPC stands for Remote Procedure Call, and the name is close to a full explanation. Your code calls a function \u2014 say That convenience hides a classic trap, though \u2014 maybe the oldest one in distributed systems. Making a remote call look like a local one papers over everything that makes networks unreliable. Martin Fowler, whose Patterns of Enterprise Application Architecture<\/em> is a standard reference here, flagged it bluntly a long time ago:<\/p>\n\n\n\n “First Law of Distributed Object Design: Don’t distribute your objects!” \u2014 Martin Fowler<\/a><\/p>\n<\/blockquote>\n\n\n\n A local function doesn’t fail because someone tripped over a cable. A remote one can, and does \u2014 latency, timeouts, requests that die half-finished. In Web3 this is a daily fact of life, because every call travels the public internet to reach a node. Build with that in mind and your integrations survive the first slow node instead of toppling over.<\/p>\n\n\n The flavor of RPC you’ll actually meet in Web3 is JSON-RPC. It’s deliberately thin \u2014 each call is a plain JSON object carrying a method name, a few parameters, an json<\/p>\n\n\n\n Read that top to bottom and you can more or less guess what it does. You’re calling Here’s a clean way to hold it in your head. The API is the whole handshake. RPC and REST are two styles for writing it \u2014 one built around actions, the other around resources. Line them up and the contrast is hard to miss:<\/p>\n\n\n\n Neither style is better in the abstract; they’re tuned for different jobs. REST shines when you’re exposing a tidy set of resources to the public web and want HTTP caching handed to you for free. RPC earns its keep when you just want to call a specific procedure with almost no overhead \u2014 which, as it happens, is exactly what talking to a blockchain feels like.<\/p>\n\n\n\n So far RPC has been one thing. But the moment someone brings up gRPC, they’re really talking about a single, souped-up version of it. Google introduced gRPC as an open-source framework in February 2015, based on Stubby \u2014 the internal RPC system it had leaned on for more than a decade. Two decisions define it. Rather than ship text like JSON, gRPC serializes data with Protocol Buffers, a compact binary format, and moves it over HTTP\/2. JSON-RPC optimizes for readability. gRPC optimizes for throughput.<\/p>\n\n\n Every RPC makes a remote function feel local. gRPC just does it with more horsepower, through three technical choices that each trade a bit of simplicity for speed:<\/p>\n\n\n\n This is where the comparison stops being hand-wavy. A widely cited benchmark by engineer Ruwan Fernando<\/a> clocked gRPC at roughly 7x faster receiving data and about 10x faster sending it against a JSON-over-HTTP setup, and a payload that runs a few hundred bytes as JSON can shrink to a fraction of that as a Protocol Buffers blob. Multiply that across millions of internal calls and the savings compound fast. That’s why gRPC became the default for service-to-service traffic at Google, and at plenty of large engineering orgs since. One catch, and it’s a big one: all of it assumes you own both ends of the connection.<\/p>\n\n\n\n Back to Web3 \u2014 where, frankly, the RPC-vs-API decision has already been made for you. Anything you want to do on-chain \u2014 check a balance, read a contract, fire off a transaction \u2014 means talking to a node somewhere. Almost nobody runs that infrastructure themselves. They connect through a hosted endpoint: a blockchain API that accepts requests and returns chain data. On Ethereum and every EVM-compatible network, that endpoint is a JSON-RPC API, spelled out in the official Ethereum JSON-RPC docs. A Web3 API, then, is mostly managed access to that JSON-RPC layer, usually with richer data endpoints stacked on top.<\/p>\n\n\n\nWhat an API Actually Is<\/h2>\n\n\n
The main flavors of API<\/h3>\n\n\n
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\/users<\/code>), reached with plain HTTP verbs: GET, POST, PUT, DELETE.<\/li>\n\n\n\n![\"\"](\"https:\/\/nownodes.io\/blog\/wp-content\/uploads\/2026\/07\/image-1024x683.png\")
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\n\n\nWhat RPC (Remote Procedure Call) Really Does<\/h2>\n\n\n
getBalance(address)<\/code> \u2014 that actually runs on a different machine, and the RPC layer hides the plumbing: packaging the request, shipping it across the network, unpacking whatever comes back. REST leans on nouns, the resources like \/blocks<\/code>. RPC leans on verbs: the action you want done. That verb-versus-noun split is what people are really circling when they pit RPC against REST.<\/p>\n\n\n\n\n
JSON-RPC, the dialect Web3 speaks<\/h3>\n\n\n
id<\/code>, and a version field. The JSON-RPC 2.0 spec<\/a> dates to 2010, built on a 2009 draft, and it hasn’t needed much since. Every EVM chain speaks it, so it’s usually the very first thing a developer touches on a network.<\/p>\n\n\n\n{\n \"jsonrpc\": \"2.0\",\n \"method\": \"eth_getBalance\",\n \"params\": [\"0xAbC...123\", \"latest\"],\n \"id\": 1\n}<\/code><\/pre>\n\n\n\neth_getBalance<\/code> with an address and a block tag; the node runs the method against the chain and returns a result tagged with the same id<\/code>. No URL scheme to memorize, no guessing \u2014 just a named function and its arguments.<\/p>\n\n\n\n
\n\n\nRPC vs API: The Difference in One Table<\/h2>\n\n\n
Feature<\/th> REST API<\/th> RPC (JSON-RPC, gRPC)<\/th><\/tr><\/thead> Design model<\/td> Resource-based (nouns like \/users<\/code>)<\/td>Action-based (verbs like getUser<\/code>)<\/td><\/tr>Typical call<\/td> GET \/users\/1<\/code><\/td>getUser(1)<\/code><\/td><\/tr>Data format<\/td> JSON, XML, and others<\/td> JSON (text) or Protocol Buffers (binary)<\/td><\/tr> Transport<\/td> HTTP<\/td> HTTP, WebSocket, or HTTP\/2<\/td><\/tr> Caching<\/td> Built into HTTP<\/td> Handled manually<\/td><\/tr> Best fit<\/td> Public web services<\/td> Internal services and blockchain calls<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
\n\n\ngRPC vs RPC: Google’s Faster Take on the Same Idea<\/h2>\n\n\n
What actually changes versus plain RPC<\/h3>\n\n\n
![\"\"](\"https:\/\/nownodes.io\/blog\/wp-content\/uploads\/2026\/07\/image-1-1024x683.png\")
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.proto<\/code> contract, so message shapes are fixed and checked at compile time.<\/li>\n\n\n\nThe performance gap, in numbers<\/h3>\n\n\n
Feature<\/th> JSON-RPC<\/th> gRPC<\/th><\/tr><\/thead> Serialization<\/td> JSON (text)<\/td> Protocol Buffers (binary)<\/td><\/tr> Transport<\/td> HTTP \/ WebSocket<\/td> HTTP\/2<\/td><\/tr> Readability<\/td> Human-readable<\/td> Not human-readable<\/td><\/tr> Setup<\/td> Minimal<\/td> Needs .proto<\/code> files and code generation<\/td><\/tr>Streaming<\/td> Via WebSockets<\/td> Native, bidirectional<\/td><\/tr> Web3 tooling<\/td> Universal<\/td> Almost none<\/td><\/tr> Best for<\/td> Blockchain and public APIs<\/td> Internal microservices<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
\n\n\nHow Web3 Actually Reaches a Blockchain<\/h2>\n\n\n