WA New Feature That I Really Like

April 24, 20244 min read

#Tech#Product Design#Messaging

i've been waiting for this. for years i've been sending messages to random group chats i made with just myself, or worse — sending stuff to my girlfriend's chat and going "ignore that, it's for me." embarrassing? yes. did it work? barely.

but now WhatsApp finally let you message yourself. and honestly it's a bigger deal than people think.

why i care

i know what you're thinking. "just use Notes app." but that's not the point. WhatsApp is already open. it's where i live. when i find a link, a screenshot, a random thought at 2 AM — i don't want to switch apps. i just want to throw it into the same place i'm already looking at.

it's like having a notebook on your desk vs one in a drawer across the room. both work. one actually gets used.

how i think they built it

this is the part that gets me excited as a developer. let's think about it.

WhatsApp uses the Signal Protocol for end-to-end encryption. every chat is between two parties with their own key pairs. so how do you create a chat with... yourself?

your phone number is both sender and receiver. the system needs to handle sender_id === receiver_id without breaking the routing logic
for encryption, in a normal chat you encrypt with the recipient's public key. here you're encrypting for your own devices. they probably use the existing multi-device architecture where each device has its own identity key
messages need to sync across all your linked devices. they likely treat it as a special conversation type in the device fanout system
on the backend it's probably just a regular chat thread with a flag. the message store doesn't care who the participants are

// simplified routing logic (pseudocode)
if (message.senderId === message.recipientId) {
  // self-chat: fanout to all user's devices
  return fanoutToAllDevices(message.senderId, message);
} else {
  // normal chat: route to recipient
  return routeToRecipient(message);
}

the real engineering challenge is making it work across devices. WhatsApp's multi-device system already handles syncing, but self-chat adds a weird loop — every device is both sender and receiver. they probably had to add deduplication logic to prevent a device from showing a message it just sent as a new incoming message. small detail, big headache.

what i use it for

since it dropped i've been using it for quick links, screenshots of stuff i need to reference, voice notes to myself (yes i talk to myself, don't judge), and draft messages before sending them to actual people. it's become my digital scratch pad. backed up, synced, searchable. everything follows me across devices.

sometimes the best features aren't revolutionary. they're just obvious things that should've existed from day one. took them long enough, but i'm glad it's here.