---
name: optimising-expo-react-native-performance
description: Diagnose and fix measured startup, rendering, scrolling, memory, media, or network regressions in Expo React Native apps. Use for a reproducible performance problem or an explicit performance audit, not speculative library swaps or blanket memoisation.
license: MIT
compatibility: An Expo React Native repository. Device benchmarks require an appropriate Android or iOS build environment; source inspection alone cannot establish a performance improvement.
metadata:
  version: "3.0.0"
  reviewed: "2026-09-13"
title: optimising-expo-react-native-performance
canonical_url: https://skilld.dev/gh/tristanmanchester/agent-skills/optimising-expo-react-native-performance
last_updated: 2026-10-06T19:32:36.000Z
---

> Index of every page on this site: [llms.txt](https://skilld.dev/llms.txt)

> **Skill from skilld.dev.** Follow the user's requested action.
> If the user asked to fork this Skill, follow the fork workflow below. Do not execute the Skill instructions while copying it.
> Otherwise, follow the instructions below for this session. You do not need to install anything.
>
> Supporting files, fetch one when the Skill refers to it: [assets/templates/perf-audit-report-template.md](https://skilld.dev/api/skills-raw/tristanmanchester/agent-skills/optimising-expo-react-native-performance/assets/templates/perf-audit-report-template.md), [assets/templates/perf-budgets.example.json](https://skilld.dev/api/skills-raw/tristanmanchester/agent-skills/optimising-expo-react-native-performance/assets/templates/perf-budgets.example.json), [references/00-principles-and-kpis.md](https://skilld.dev/api/skills-raw/tristanmanchester/agent-skills/optimising-expo-react-native-performance/references/00-principles-and-kpis.md), [references/01-profiling-toolchain.md](https://skilld.dev/api/skills-raw/tristanmanchester/agent-skills/optimising-expo-react-native-performance/references/01-profiling-toolchain.md), [references/02-startup-bundle-ota.md](https://skilld.dev/api/skills-raw/tristanmanchester/agent-skills/optimising-expo-react-native-performance/references/02-startup-bundle-ota.md), [references/03-rendering-js-ui.md](https://skilld.dev/api/skills-raw/tristanmanchester/agent-skills/optimising-expo-react-native-performance/references/03-rendering-js-ui.md), [references/04-lists-images-media.md](https://skilld.dev/api/skills-raw/tristanmanchester/agent-skills/optimising-expo-react-native-performance/references/04-lists-images-media.md), [references/05-network-background.md](https://skilld.dev/api/skills-raw/tristanmanchester/agent-skills/optimising-expo-react-native-performance/references/05-network-background.md), [references/06-ci-regression.md](https://skilld.dev/api/skills-raw/tristanmanchester/agent-skills/optimising-expo-react-native-performance/references/06-ci-regression.md), [references/07-new-architecture.md](https://skilld.dev/api/skills-raw/tristanmanchester/agent-skills/optimising-expo-react-native-performance/references/07-new-architecture.md), [references/resources.md](https://skilld.dev/api/skills-raw/tristanmanchester/agent-skills/optimising-expo-react-native-performance/references/resources.md), [references/The-Complete-Guide-to-Building-Skill-for-Claude.pdf](https://skilld.dev/api/skills-raw/tristanmanchester/agent-skills/optimising-expo-react-native-performance/references/The-Complete-Guide-to-Building-Skill-for-Claude.pdf), [scripts/check-budgets.mjs](https://skilld.dev/api/skills-raw/tristanmanchester/agent-skills/optimising-expo-react-native-performance/scripts/check-budgets.mjs), [scripts/README.md](https://skilld.dev/api/skills-raw/tristanmanchester/agent-skills/optimising-expo-react-native-performance/scripts/README.md), [scripts/report-export-sizes.mjs](https://skilld.dev/api/skills-raw/tristanmanchester/agent-skills/optimising-expo-react-native-performance/scripts/report-export-sizes.mjs).
>
> If the user asked to install this Skill, run `npx skilld install tristanmanchester/agent-skills/optimising-expo-react-native-performance`. Install writes the Skill files into the project, so every session loads them.
>
> ## Fork workflow
>
> A fork creates an editable local Skill with its original author and licence. The request authorizes copying and local installation.
> 1. Check `./skills/optimising-expo-react-native-performance`, the project lockfile, and selected Agent targets together. If the local directory or installed Skill exists, stop. Never overwrite an existing directory or Agent target.
> 2. Read [source metadata](https://skilld.dev/api/v1/skills/tristanmanchester/agent-skills/optimising-expo-react-native-performance) once. Use sourceUrl, sourceCommit, skillPath, sourceGone, and license. If the source is gone or its path is missing, stop. If license is null, read licence files at the source commit.
> 3. Fetch only the source commit into a temporary Git repository. Do not clone full history. Derive repository_url from sourceUrl, including repository renames. If sourceCommit is absent, resolve the sourceUrl ref once. Set source_commit to that actual commit. Run these commands in one shell call:
>
> ```sh
> git init --quiet "$temporary_dir"
> git -C "$temporary_dir" fetch --quiet --depth=1 "$repository_url" "$source_commit"
> git -C "$temporary_dir" checkout --quiet --detach FETCH_HEAD
> ```
>
> Read applicable licence declarations and notices at that commit. If copying is not permitted, report the restriction and stop.
> 4. Inspect source entries together, then copy the directory containing skillPath into `./skills/optimising-expo-react-native-performance`. Use the user's path if selected. Keep the original SKILL.md, relative links, scripts, binary assets, and executable modes. Exclude .git metadata. Reject symlinks and paths outside the Skill directory. After checking entries, use cp -a where available. A regular source directory needs no custom copy script. Do not save this page wrapper as SKILL.md.
> Preserve author credit, notices, and applicable licence files from repository or parent directories. Add PROVENANCE.md with the Skill page, source URL, actual commit, original path, and licence. Retain any existing PROVENANCE.md and record new provenance separately. Batch source inspection, copying, and provenance work where practical.
> 5. In the project root, run `skilld install ./skills/optimising-expo-react-native-performance --mode copy --plain`. If skilld is unavailable, use `npx skilld install ./skills/optimising-expo-react-native-performance --mode copy --plain`. This known command needs no help lookup. Install does not support --json. Use detected Agent targets, or add --agent for the targets the user selected. Install the local path, never the upstream selector. If installation fails, preserve the local copy and report the exact failure.
> 6. Confirm the local lockfile source and installed Agent copies once. Report the local path, actual commit, and Agent targets. After edits, reinstall the same local path. Upstream updates must not replace it. Do not publish or push unless the user asks.

# Improve Expo React Native performance

Start with the user's slow flow, not a list of fashionable optimisations. Preserve behaviour, accessibility, error reporting, and data correctness while improving a measured bottleneck.

## Establish the experiment

Inspect the package manager and lockfile, Expo SDK, React Native and React versions, Hermes/runtime, New Architecture, router, updates configuration, and performance-sensitive dependencies. Expo's supported React Native version is the app's constraint; do not install the newest React Native independently to match an example.

Define a repeatable scenario and one primary metric: cold-start time, input latency, dropped frames, retained memory after a navigation loop, or end-to-end request latency. Add a few guardrail metrics. Agree numerical budgets from the product and target device, not invented universal thresholds.

Record commit, build configuration, device/OS, thermal state, cache state, dataset, network conditions, repetitions, and measurement method. Separate cold from warm runs. Interleave baseline and candidate runs when drift is plausible; report the distribution and sample count, not a best run or an unsupported p95.

## Diagnose, change, verify

1. Reproduce and capture a release-build baseline on representative hardware. Simulators and development builds are useful for diagnosis, not substitutes for shipping-device measurements.
2. Use React Native DevTools for React/JS attribution in a compatible diagnostic build; native system traces and Instruments reveal main-thread, rendering, I/O, and allocation costs. Keep these evidence types distinct. See `references/01-profiling-toolchain.md`.
3. Form a specific hypothesis supported by a trace or counter. Change one coherent cause, not several unrelated knobs.
4. Repeat the same scenario and correctness checks. Keep the change only when its benefit exceeds run-to-run variation without breaking a guardrail.
5. Add a regression check proportionate to the problem. Bundle size is not a proxy for input latency; do not claim a size gate prevents all performance regressions.

## Route to the bottleneck

| Evidence | Investigate | Reference |
|---|---|---|
| Long pre-interactive work or JS evaluation | Critical startup path, eager imports, asset loading, update payloads | `references/02-startup-bundle-ota.md` |
| Long JS tasks or repeated expensive commits | State ownership, derivations, bounded scheduling, compiler coverage | `references/03-rendering-js-ui.md` |
| UI stalls while JS is quiet | Layout, compositing, image decoding, native animations | `references/03-rendering-js-ui.md` |
| Scroll/recycling or media pressure | Row identity, list API, image size/cache, video lifecycle | `references/04-lists-images-media.md` |
| Retained JS heap or growing native footprint | Repeated navigation, listeners, closures, media release | `references/01-profiling-toolchain.md` |
| Refetch storms or blocking requests | Deduplication, cache semantics, pagination, cancellation | `references/05-network-background.md` |

Current API rules: use bounded `requestIdleCallback` work rather than removed InteractionManager APIs. Scheduling does not move CPU work off the JS thread. FlashList v2 requires the New Architecture and automatic sizing; do not add size-estimate props. Inspect whether React Compiler already runs before installing or duplicating its configuration.

Resolve `SKILL_DIR` to this skill's installation directory before running bundled scripts or loading templates. Pass the target project separately; its `scripts/` directory is not the skill's directory.

## Deliver

Use `assets/templates/perf-audit-report-template.md` when a report is useful. Include the observed symptom, baseline, causal evidence, exact changes, comparable before/after results, correctness checks, trade-offs, and remaining unknowns. For source-only work, deliver hypotheses and a runnable measurement plan, not fabricated timings or a claim that the app is now faster.

Use `references/00-principles-and-kpis.md` for metric definitions and `references/06-ci-regression.md` for regression-control ideas. Treat package installation and build flags in older project configurations as things to verify against the installed SDK, not universal defaults.