Threads: Instagram's Text-Sharing App on iOS, Android and Web

Threads is described by its makers as a new app for sharing text updates and joining public conversations, built by the Instagram team. Official development of the iOS version started in early 2023, and the app was unveiled publicly on 5 July after roughly five months of technical work. The team set out to deliver an app that might not have many features at launch but did the things it did well, noting that expectations of a new app from Meta may be higher than those for an app from a new startup.

• Built by the Instagram team
• Text updates and public conversations
• iOS development began in early 2023
• Unveiled on 5 July

Threads spans three platform cores: iOS, Android and a read-only web experience. The web version was initially read-only so the team could confirm it was solving a real problem before investing further; it supported link sharing and allowed people to view content without needing an account. A fuller web version shipped a month after the app launch, which the team attributes in part to community support.

• iOS
• Android
• Read-only web at launch, supporting link sharing without an account
• Web version shipped a month after launch

Each platform core was staffed by a small group of engineers, with other teams and individuals asked to volunteer part of their time. Keeping the team small helped it stay nimble in the face of evolving designs and decisions, and also helped keep the project under wraps. Separately from day-to-day app work, about a dozen engineers worked on the feed-ranking models often referred to as "the algorithm" and on the integrity systems intended to keep Threads a place where people would want to be. Engineers already familiar with the codebase could move quickly, while the team also sought engineers with strong product sensibility who could work independently.

• Small core teams per platform
• Volunteer time from other teams
• About a dozen engineers on feed ranking and integrity

On iOS, Threads is at its core the Instagram app launched with a different app delegate. The team uses Buck2, a distributed-caching, large-scale build tool, for code modularity, including generating an .xcodeproj file from a given set of libraries. The app delegate, UIApplicationDelegate, acts as the overarching coordinator that starts the app and interfaces with the system to handle events such as launch. The write-up also covers list handling considerations including object uniqueness in IGListKit, caching with IGMedia objects as a single source of truth, and the rule that all posts belong to a thread.

• Instagram app with a different app delegate
• Buck2 build tool for code modularity
• IGListKit object uniqueness
• IGMedia objects as a single source of truth
• Every post belongs to a thread

The account of building Threads for iOS is published as an article on the @Scale Conferences site, dated 2023 and credited to the @Scale team. The page is titled "Making Threads for iOS: Unraveling Our Journey from 0 to 1" and is presented as a deep dive into the app's development. It sits alongside other engineering articles on the same site, such as material on reliability engineering at Meta.

• Published on atscaleconference.com
• Article type, year 2023
• Credited to the @Scale team