OFFSIDE is a social app for close friends only. Shake phones together and you're friends.

What you can do

Shake to add friends — shake together in the same place and you're friends.
Your space — decorate it with backgrounds and stickers, and keep photos, diaries, links and places in one spot.
Diary — write about your day and choose who sees it: just you, or the friends you pick.
Photos — decide who can view and comment on each album.
Chat & Drop — talk 1:1 with friends. Conversations aren't stored permanently on our servers.
Guestbook — leave a note on a friend's space.

Safe to use

14+ only.
You decide what to share, and with whom.
Block and report any person or post.
Delete your account anytime in Settings.

Availability

OFFSIDE is available on the App Store for iPhone and on Google Play for Android, in Korean, English, Japanese and Chinese.

How we build

OFFSIDE is built and run by a solo founder in Seoul. Development started in May 2025. We build it with Claude Code, from features and tests to releases, store submissions and security reviews.

Our story

OFFSIDE started in May 2025 in Seoul as a side project by Donghouk Shin, built around one idea: friends should be people you have actually met. The first public version shipped to Google Play and the App Store in mid-2026 under the name Casti, the business was registered in Seoul on January 19, 2026, and the app was renamed OFFSIDE in September 2026 when it moved to offside.my. It is still maintained by the same founder.

Company

Company name: 오프사이드(OFFSIDE)
Business type: Sole proprietorship registered in the Republic of Korea
Business registration number: 165-09-03272
Registered: January 19, 2026
Representative: Donghouk Shin (신동혁)
Location: Seoul, South Korea
Email: contact@offside.my
Website: offside.my

About OFFSIDE