[Due for payment 2026-03-06] [$250] [Performance] Attachments/images load extremely slowly when viewing in the app

[mountiny]

Problem

Attachments and images load very slowly when viewing them in the app, with reports of nearly a minute to load a single low-resolution image even on fast internet connections.

Observations

• On mobile (iOS), loading a single attachment can take ~1 minute for a low-res image
• Web loads faster than mobile, but still slower than expected for a responsive application
• User's internet is fast and everything else loads fine
• The issue is reproducible and was observed by multiple team members during Onshore

Suspected Cause

The attachment carousel feature may be preloading all images in the chat to enable the < and > navigation arrows. For chats with many attachments, this means:

1. Opening one image triggers loading of potentially dozens/hundreds of other images
2. This causes significant delays before the requested image is visible
3. Large/active chats are disproportionately affected

Expected Behavior

• The selected attachment should load within 1-2 seconds on a decent internet connection
• If carousel preloading is needed, it should happen lazily/progressively after the primary image is loaded
• Adjacent images (prev/next) could be prioritized over distant ones

Reproduction Steps

1. Open a chat with many attachments/images
2. Tap on an attachment to view it in the full-screen viewer
3. Observe the loading spinner duration

Platform

• iOS (primary report)
• Android (needs verification)
• Web (also affected but less severe)

Related Discussion

Slack thread: https://expensify.slack.com/archives/C05LX9D6E07/p1770083248855669

Possible Solutions

1. Lazy carousel loading: Only preload adjacent images (N-1, N+1) initially, then progressively load others
2. Show image immediately: Display the requested image first, then load carousel images in background
3. Thumbnail fallback: Show low-res thumbnails for carousel navigation while full-res images load on demand
4. Limit preload count: Cap the number of images preloaded for the carousel

Upwork Automation - Do Not Edit

• Upwork Job URL: https://www.upwork.com/jobs/~022018561992008864454
• Upwork Job ID: 2018561992008864454
• Last Price Increase: 2026-02-03
• Automatic offers:
• abzokhattab | Reviewer | 110396511

[melvin-bot]

Triggered auto assignment to @laurenreidexpensify (Bug), see https://stackoverflow.com/c/expensify/questions/14418 for more details. Please add this bug to a GH project, as outlined in the SO.

[melvin-bot]

Job added to Upwork: https://www.upwork.com/jobs/~022018561992008864454