Skip to content
Visit Miniflare on GitHub
Set theme to dark (โ‡ง+D)

๐Ÿ“ฆ KV


Specify KV namespaces to add to your environment as follows:

kv_namespaces = [
{ binding = "TEST_NAMESPACE1", id = "<ignored>", preview_id = "<ignored>" },
{ binding = "TEST_NAMESPACE2", id = "<ignored>", preview_id = "<ignored>" }
const mf = new Miniflare({

You can now access KV namespaces in your workers:

Service Worker
addEventListener("fetch", (event) => {
TEST_NAMESPACE1.get("key").then((value) => new Response(value))
export default {
async fetch(request, env) {
return new Response(await env.TEST_NAMESPACE1.get("key"));

Miniflare supports all KV operations and data types. Whilst it accepts the cacheTtl options, it is ignored since there's only one "edge location" (the user's computer) so it doesn't really mean anything.


Like the real Workers runtime, Miniflare will throw errors when:

  • Keys are empty, ., .., undefined, or greater than 512B when UTF-8 encoded
  • Values are greater than 25MiB
  • Metadata is greater than 1KiB
  • The cacheTtl option is less than 60s
  • The expirationTtl option is non-numeric, less than or equal 0, or less than 60s
  • The expiration option is non-numeric, less than or equal the current time, or less than 60s in the future
  • The limit passed to KVNamespace#list() is non-numeric, less than or equal 0, or greater than 1000

Manipulating Outside Workers

For testing, it can be useful to put/get data from KV outside a worker. You can do this with the getKVNamespace method:

import { Miniflare } from "miniflare";
const mf = new Miniflare({
modules: true,
script: `
export default {
async fetch(request, env, ctx) {
const value = parseInt(await env.TEST_NAMESPACE.get("count")) + 1;
await env.TEST_NAMESPACE.put("count", value.toString());
return new Response(value.toString());
kvNamespaces: ["TEST_NAMESPACE"],
const ns = await mf.getKVNamespace("TEST_NAMESPACE");
await ns.put("count", "1");
const res = await mf.dispatchFetch("http://localhost:8787/");
console.log(await res.text()); // 2
console.log(await ns.get("count")); // 2