Items can vary in level; most current codes give items the same level as the agent (up to L 8). Mods and other non-level items are usually between Common and Rare mods. Very few passcodes give out Very Rare items like the JARVIS Virus, Capsule, etc.
Passcodes can be found hidden in various Ingress and Niantic Releases. The original source of them was P. A. Chapeau's The Sphere of Weirdness, a blog found at nianticproject.com. Passcodes were hidden as ciphers, hidden as pixels in an image, or sometimes in plaintext. Passcodes can also be found in Google+ releases from several sources; some of the developer's private blogs, Ingress' official G+, and some other pages like Verum Inveniri, which has been releasing a series of puzzles in the form of mysterious postcards.
Passcodes are a public release, and lists of them are documented on many sites. But in order to keep the codes by being over-used, Ingress puts both an expiration date and a use counter on most passcodes. Depending on where a passcode is gotten from, and what it contains, they can have longer or shorter availability.
The age of a passcode can often be inferred by its encryption scheme. The newest passcodes (as of Feb 2015) are in the format:
A short series of passcodes released in January followed the format:
However, most passcodes you will find on the internet (as of Aug 2015) will have the following format:
Older ones may be along the lines of X74F6O6YE9, creative91h, 5we7kurezet2s3u, and others. Many of these are expired.
Use EditPasscodes can be entered in the Scanner app via the OPS area using the "Passcode" tab. This option is not available on the iPhone or iOS devices, those users can redeem only via the Intel Map.
In the Ingress Intel Map online, use the "Passcode" link above the location search in the upper right hand corner of the map. However, overuse of this will result in overheating and a time limit will be set before further use can be had. This cooldown does not affect the Scanner.
The following messages may appear when attempting to redeem a passcode:
|"Passcode fully redeemed"||The passcode you’re attempting to use has expired or its limit has been reached. Frequently shortened to FR in chats.|
|"Passcode already redeemed"||You personally have already used this passcode. The passcode is still valid for other agents who have not used it.|
|"Invalid passcode"||The passcode you’ve attempted to enter is not typed correctly or is not a passcode.|
|"Passcode circuitry too hot. Wait for cool down to enter another passcode."
(Only on Intel Map)
|Too many passcodes used in a short time. The Agent should wait some time before redeeming any more codes. According to community analysis, this is somewhere around 30 minutes, but not consistently.|
|"XM object capacity reached."||Your inventory is full. Try to free up some space before entering a passcode.|
|"Passcode cannot be redeemed."||There's a temporary error with this passcode, try again later. (Does anyone know the reason for this?)|
Working Passcodes Edit
Here is a list of passcodes known to be working as of 3 February 2019.
26 November 2018:
End of Year Passcodes (2018)