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memdown LevelDB Logo

In-memory abstract-leveldown store for Node.js and browsers.

Travis Coverage Status npm npm Greenkeeper badge


levelup allows you to pass a db option to its constructor. This overrides the default leveldown store.

// Note that if multiple instances point to the same location,
// the db will be shared, but only per process.
var levelup = require('levelup')
var db = levelup('/some/location', { db: require('memdown') })
db.put('hey', 'you', function (err) {
  if (err) throw err
    .on('data', function (kv) {
      console.log('%s: %s', kv.key, kv.value)
    .on('end', function () {

Your data is discarded when the process ends or you release a reference to the database. Note as well, though the internals of memdown operate synchronously - levelup does not.

Running our example gives:

hey: you

Browser support

Sauce Test Status

memdown requires a ES5-capable browser. If you're using one that's isn't (e.g. PhantomJS, Android < 4.4, IE < 10) then you will need es5-shim.

Global Store

Even though it's in memory, the location parameter does do something. memdown has a global cache, which it uses to save databases by the path string.

So for instance if you create these two instances:

var db1 = levelup('foo', {db: require('memdown')});
var db2 = levelup('foo', {db: require('memdown')});

Then they will actually share the same data, because the 'foo' string is the same.

You may clear this global store using memdown.clearGlobalStore():


By default, it doesn't delete the store but replaces it with a new one, so the open instance of memdown will not be affected.

clearGlobalStore takes a single parameter, which if truthy clears the store strictly by deleting each individual key:

require('memdown').clearGlobalStore(true); // delete each individual key

If you are using memdown somewhere else while simultaneously clearing the global store in this way, then it may throw an error or cause unexpected results.


In addition to the regular npm test, you can test memdown in a browser of choice with:

npm run test-browser-local

To check code coverage:

npm run coverage


memdown is Copyright (c) 2013-2017 Rod Vagg @rvagg and licensed under the MIT licence. All rights not explicitly granted in the MIT license are reserved. See the included LICENSE file for more details.