What does Monzo do with my contacts?
We never send or store your full address book on our servers and we wonât spam or get in touch with your contacts without your permission, nor share their information outside of Monzo. If youâre interested in the details, you can read more below.
What do people see when I pay them?
Anyone you send money to from within the Monzo app will see your name, any message you added, and the amount of the payment. Additionally, those who donât already have your phone number will be able to see your number and add it to their address book so they can send money back to you.
The details
We wanted to build Monzo payments in the most privacy friendly way we could, whilst still making it as simple and easy to use for our customers as possible. We never send or store your full address book on our servers, instead we use the following process to check if your contacts already use Monzo:
- Your device generates a hash for each of the contacts in your address book
- Your device then uploads a portion of that hash to the Monzo servers
- The server checks if the hash matches any existing users and if it does, sends your device a slightly larger portion of the hashed contact
- Your device then matches the larger hash with its existing hash to confirm the correct contact record has been matched
- If thereâs a match, we show you that contact as a Monzo contact. If thereâs no match, the hash is deleted from the server and Monzo never sees any of the contactâs information.
- The server never receives any of your contactsâ phone numbers, names or any other personal details during this process. The only time we transmit their full phone number is when you actually send money to that person and this is fully encrypted in transit, stored securely as part of our banking infrastructure, and only sent once youâve confirmed the payment using your PIN or fingerprint.
I have other questions
Weâd love to chat! Message us through the in-app chat with your thoughts, questions and feedback.
That hashed contact check sounds awesome, good work!
What is the âLocation-based securityâ toggle switch?
I would assume if your phone is in the UK and a transaction comes up in europe Monzo would look a bit closer at the actual transaction regarding a fraudulent transaction
This is a truly excellent explanation, thank you.
In the future, is there any chance of these kinds of security and privacy explanations being compiled into an easily linkable support page/document? Thinking along the lines of Appleâs iOS security documents. It nicely fills that gap between the more marketing messages and revealing exact implementation details, a huge step to being transparent (and more importantly, understandable) about whatâs going on with user data IMO.
The update sounds great. The âWhatâs Newâ message in the App Store ⌠not so much. A couple weeks ago the jokes might have worked, but this week itâs too raw. Please reconsider.
Thanks for designing with privacy in mind from the beginning. Privacy is the biggest concern I have with a lot of new services. If not considered from the outset, you either end up with something that is a hassle/inconvenient to use, or something that has no regard for keeping my data private. Iâm very glad to see the Monzo team thinking this through and building a good foundation!
Having just updated the Monzo app and checking out the contacts tab, I have a suggestion for improving this feature. Could you add the option to filter the contacts list to just those who are already on Monzo? If I want to see whether I can send a friend money, Iâm not going to invite them to Monzo. I might later, but at that moment, I want to see if I can send it through Monzo (and then do it), and if not Iâll sort it out another way. Inviting friends to use Monzo is a separate action and I feel that it currently subverts the usefulness of the Contacts tab. My contacts list is way too long to scroll through to find out who I can send 
to!
Iâd like to know what the location-based security switch does as well. Canât find an explanation on these forums. What are the implications of enabling it?
Anyone youâre able to send money to (i.e. whoâs already enabled Payments with Friends) will already appear at the top of the Contacts list, so you donât have to scroll through to find them 
I definitely think that âAll Contactsâ, which for me is full of hundreds of random people, could be hidden behind a âShow all contactsâ button, for clarityâs sake.
Ah, my mistake â thanks @ned. In that case, the contacts of mine who I know have :mondo: either havenât updated their app yet, or havenât enabled the Send Money feature. Good to know they will appear at the top when they do. 
In the interest of privacy, some of us may not want our contacts to have our phone number. Contacts arenât just close friends and relatives. They might be companies, they can be imported from Facebook, Twitter, can be manually entered and just contain an email or postal address, plus Iâm sure there are other scenarios.
I understand itâd be a lot more work and weâre all keen to see the launch of the current account, but Iâd like to see the iOS Contacts app (plus Android if itâs possible) extended with a Monzo integration. Instead of sharing our phone number it could share our Monzo user ID or perhaps a unique public token that we share with contacts if the user ID is meant to be kept secret.
@beningreenjam Donât worry, your contacts donât get your phone number. The only time someone will get your phone number is if you send a payment to them (using their phone number)
I would like to write a comprehensive Security post that details all of those things at some point. Iâd like to finalise the details around account recovery and authentication before I write this though.
Hope this is the best place for this pedantic bug report. Iâm on iOS, v1.9.1.
In the Contacts tab, the âContacts on Monzoâ, and âAll Contactsâ headers are currently pinned to the viewport rather than the list below - so they remain visible when scrolling and overlap contact names. Could this be changed so that they scroll out of sight as expected?
A single list header remains visible while youâre scrolling, right? I wouldnât expect it to scroll out of site personally, I think this is a design choice & it doesnât get in the way for me (on an iPhone 6S)âŚ
Hi Alex, thanks for the screenshot - leads me to wonder whether the fact Iâm still on iOS 9.3.3 is the issue - I donât have the white âheader rowâ behind All Contacts - itâs simply transparent, which doesnât look great when it overlaps with contact names. Screenshot here.
Is your phone jailbroken?
Nope. iPhone SE, on vanilla 9.3.3 (by choice - avoiding iOS 10 for the moment!).