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    2.0.0-beta.1 • Public • Published


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    Simple cookie-based session storage for micro.

    Actually, a tiny a wrapper for the excellent express middleware.


    This is a Node.js module available through the npm registry. Installation is done using the npm install command:

    $ npm install micro-cookie-session


    // import micro
    const micro = require('micro')
    // initiallise session
    const session = require('.')({
      name: 'session',
      keys: ['someverystringsecretstring'],
      maxAge: 24 * 60 * 60 * 1000
    // set up micro server
    const server = micro((req, res) => {
      // enable session storage in cookie
      session(req, res)
      // store start time and current time in session
      req.session.demoFirstHit = req.session.demoFirstHit || new Date() * 1
      req.session.demoLastHit = new Date() * 1
      // display milliseconds since session started
      return `Session started ${req.session.demoLastHit - req.session.demoFirstHit}ms ago`
    // fire it up


    Create a new cookie session instance with the provided options. This function will attach the property session to req, which provides an object representing the loaded session. This session is either a new session if no valid session was provided in the request, or a loaded session from the request.

    The function will automatically add a Set-Cookie header to the response if the contents of req.session were altered. Note that no Set-Cookie header will be in the response (and thus no session created for a specific user) unless there are contents in the session, so be sure to add something to req.session as soon as you have identifying information to store for the session.


    Micro cookie session accepts these properties in the options object (identical to the cookie-session express middleware).


    The name of the cookie to set, defaults to session.


    The list of keys to use to sign & verify cookie values. Set cookies are always signed with keys[0], while the other keys are valid for verification, allowing for key rotation.


    A string which will be used as single key if keys is not provided.

    Cookie Options

    Other options are passed to cookies.get() and cookies.set() allowing you to control security, domain, path, and signing among other settings.

    The options can also contain any of the following (for the full list, see cookies module documentation:

    • maxAge: a number representing the milliseconds from for expiry
    • expires: a Date object indicating the cookie's expiration date (expires at the end of session by default).
    • path: a string indicating the path of the cookie (/ by default).
    • domain: a string indicating the domain of the cookie (no default).
    • sameSite: a boolean or string indicating whether the cookie is a "same site" cookie (false by default). This can be set to 'strict', 'lax', or true (which maps to 'strict').
    • secure: a boolean indicating whether the cookie is only to be sent over HTTPS (false by default for HTTP, true by default for HTTPS). If this is set to true and Node.js is not directly over a TLS connection, be sure to read how to setup Express behind proxies or the cookie may not ever set correctly.
    • httpOnly: a boolean indicating whether the cookie is only to be sent over HTTP(S), and not made available to client JavaScript (true by default).
    • signed: a boolean indicating whether the cookie is to be signed (true by default). If this is true, another cookie of the same name with the .sig suffix appended will also be sent, with a 27-byte url-safe base64 SHA1 value representing the hash of cookie-name=cookie-value against the first Keygrip key. This signature key is used to detect tampering the next time a cookie is received.
    • overwrite: a boolean indicating whether to overwrite previously set cookies of the same name (true by default). If this is true, all cookies set during the same request with the same name (regardless of path or domain) are filtered out of the Set-Cookie header when setting this cookie.


    Represents the session for the given request.


    Is true if the session has been changed during the request.


    Is true if the session is new.


    Determine if the session has been populated with data or is empty.


    Represents the session options for the current request. These options are a shallow clone of what was provided at initialisation and can be altered to change cookie setting behavior on a per-request basis.

    Destroying a session

    To destroy a session simply set it to null:

    req.session = null


    Further examples can be seen in express middleware but have not been tested (please report any micro related issues).

    Usage Limitations

    Max Cookie Size

    Because the entire session object is encoded and stored in a cookie, it is possible to exceed the maxium cookie size limits on different browsers. The RFC6265 specification recommends that a browser SHOULD allow

    At least 4096 bytes per cookie (as measured by the sum of the length of the cookie's name, value, and attributes)

    In practice this limit differs slightly across browsers. See a list of browser limits here. As a rule of thumb don't exceed 4093 bytes per domain.

    If your session object is large enough to exceed a browser limit when encoded, in most cases the browser will refuse to store the cookie. This will cause the following requests from the browser to either a) not have any session information or b) use old session information that was small enough to not exceed the cookie limit.

    If you find your session object is hitting these limits, it is best to consider if data in your session should be loaded from a database on the server instead of transmitted to/from the browser with every request. Or move to an alternative session strategy.






    npm i micro-cookie-session

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