Gmail plus addressing: how the + trick works

How the Gmail plus trick works

Gmail ignores everything between a + and the @ when it decides where to deliver a message. So name+news@gmail.com, name+travel@gmail.com and name+x7k@gmail.com all land in the inbox of name@gmail.com. The part after the + is usually called a tag, and it can be a word, a code, or a jumble of letters and numbers.

There is nothing to create or switch on. Every Gmail address accepts tags already, and you can make a new one up on the spot while filling in a form. The + is a valid character in an email address under the standards that define them, so a correctly built form has no reason to refuse it.

What makes it useful is that the tag is kept. Delivery ignores it, but the message still shows the exact address it was sent to, tag and all, so you can see it and sort by it later.

Using + aliases to filter and track mail

Because the tag stays on the address a message was sent to, you can sort mail by it and see who used it. In Gmail, create a filter on the To field with the full tagged address, such as name+news@gmail.com, and have it apply a label, mark the mail as read or skip the inbox. Everything you signed up for with +news is then filed for you.

Tracking works the same way. Give each site its own tag, such as +shopname or +airline, and if mail starts arriving at a tag you only gave to one company, you know where your address went. It is a strong clue rather than proof, but it is usually enough to know who to unsubscribe from.

Developers use it for testing too: one real inbox, a new tag for every test run, and every welcome email or password reset landing somewhere you can check it.

Why some sites reject a + in an email address

Some sites reject it because their form checks addresses too strictly, and some because they know exactly what it is. The first group is the carelessly built form. A check that allows only letters, numbers, dots and dashes before the @ will refuse a perfectly valid address. Older systems can also mangle a +, because in a web address a + is often read as a space, so what gets saved is not what you typed.

The second group does it on purpose. A site that allows one account or one free trial per address knows a + makes a new-looking address in seconds, so it either refuses the form or strips the tag before comparing addresses. Some strip it without telling you, which quietly defeats tracking: the mail still arrives, just without the tag.

If a form refuses a +, the dots style is the usual way round it, because dots look like part of an ordinary name.

Plus addressing vs the dot trick

Both make one Gmail inbox answer to many addresses, but a + labels the mail while dots disguise the address. A + alias announces itself. Anyone who knows Gmail can see the tag and remove it, which is why sites that want to block aliases look for the + first. In return, the tag tells you which alias, and so which site, a message came through.

Dots work the other way round. Gmail ignores them, so they read like an ordinary name and get past forms that refuse a +, but dot arrangements are hard to tell apart at a glance and make poor filters. The Gmail dot trick guide covers how those work. In short: use a + when you want to sort mail, and dots when a form will not take one.

Generating plus addresses here

Choose the Gmail +plus style and press Generate, and you get a tagged address on a shared account with its inbox on this page. Addresses look like user+x7k@gmail.com. They are real gmail.com addresses, so mail sent to them arrives and can be read here without signing in to anything, and any verification code is picked out and shown beside the message, ready to copy.

If a form refuses the +, switch to the dots or Googlemail style and generate again. For testing, bulk makes up to 500 addresses at once, to copy or download as a .txt file, for one request.

Remember that these are shared accounts, not yours: on a public address, anyone who knows it can read its mail. To tag your own Gmail you do not need this site at all — just add the + yourself.