Fork me on GitHub

Coverage Status



What is web4?

How it works?

You only need to deploy single smart contract using WebAssembly to host your app HTTP backend, static resources and blockchain logic.

There is an HTTP gateway to NEAR blockchain which allows smart contract to handle arbitrary GET requests.

Every smart contract on NEAR also gets corresponding API endpoint which can be accessed through regular HTTP requests.

Known web4 sites

Useful tools

Example contract (in AssemblyScript)

export function web4_get(request: Web4Request): Web4Response {
    if (request.path == '/test') {
        // Render HTML with form to submit a message
        return htmlResponse(form({ action: "/web4/contract/guest-book.testnet/addMessage" }, [
            textarea({ name: "text" }),
            button({ name: "submit" }, ["Post"])

    if (request.path == '/messages') {
        const getMessagesUrl = '/web4/contract/guest-book.testnet/getMessages';
        // Request preload of dependency URLs
        if (!request.preloads) {
            return preloadUrls([getMessagesUrl]);

        // Render HTML with messages
        return htmlResponse('messages: ' + util.bytesToString(request.preloads.get(getMessagesUrl).body)!);

    if (request.accountId) {
        // User is logged in, we can welcome them
        return htmlResponse('Hello to <b>' +  request.accountId! + '</b> from <code>' + request.path + '</code>');

    // Demonstrate serving content from IPFS
    if (request.path == "/") {
        return bodyUrl('ipfs://bafybeib72whzo2qiore4q6sumdteh6akewakrvukvqmx4n6kk7nwzinpaa/')

    // By default return 404 Not Found
    return status(404);

Basically smart contract just needs to implement web4_get method to take in and return data in specific format.


class Web4Request {
    accountId: string | null;
    path: string;
    params: Map<string, string>;
    query: Map<string, Array<string>>;
    preloads: Map<string, Web4Response>;


class Web4Response {
    contentType: string;
    status: u32;
    body: Uint8Array;
    bodyUrl: string;
    preloadUrls: string[] = [];
    cacheControl: string;

Loading data

You can load any required data in web4_get by returning list of URLs to preload in preloadUrls field.

E.g. contract above preloads /web4/contract/guest-book.testnet/getMessages. This class getMessages view method on guest-book.testnet contract.

After data is preloaded web4_get gets called again with loaded data injected into preloads.

Posting transactions

You can post transaction by making a POST request to corresponding URL.

E.g contract above preloads has form that gets posted to /web4/contract/guest-book.testnet/addMessage URL. This URL submits transaction which calls addMessage method on guest-book.testnet contract.

Note that both JSON and form data are supported. When transaction is processed by server user gets redirected to wallet for signing this transaction.

In future there is a plan to allow sending app-specific key as a cookie to sign limited subset of transactions without confirmation in wallet.

Caching considerations

By default all HTML responses can be cached for 1 minute (assumed dynamic content). All images, videos, audio and CSS can be cached for 1 day (assumed static content).

You can override this by setting cacheControl field in response.

It's not recommended to cache content for too long as then it not going to be hot on IPFS gateway.

Rust support

Check out sample web4 project made with Rust.

You can access your deployed smart contract on This is hosted web4 gateway provided to all .near accounts. For now it's free, but in future you might have to pay depending on how much traffic you get.

Every contract gets corresponding domain, e.g. check out rendered by web4.near contract.

This works same as but for contracts deployed on testnet. Every account.testnet gets corresponding domain.

Running locally

  1. Install mkcert.
  2. Install local certificate authority (this allows browser to trust self-signed certificates):
    mkcert -install
  3. Create * SSL certificate:
    mkcert "*"
  4. Run web4 man-in-the-middle proxy locally:
    IPFS_GATEWAY_URL= NODE_ENV=mainnet WEB4_KEY_FILE=./ WEB4_CERT_FILE=./ npx web4-near
  5. Setup browser to use automatic proxy configuration file at http://localhost:8080/ or to use localhost:8080 as an HTTPS proxy server.

Environment variables


This project aims to make trade offs based on these priorities: