Flutter keeps an SDK, a pub cache and a build folder per project

Flutter is generous with disk in three places at once, and clearing one does nothing for the other two. Knowing which is which turns a vague several gigabytes into three specific numbers.

The three places

flutter doctor -v | Select-String 'Flutter version|Framework|Engine'
Get-ChildItem "$env:LOCALAPPDATA\Pub\Cache","$env:USERPROFILE\flutter" -EA SilentlyContinue |
  ForEach-Object {
    $s = (Get-ChildItem $_.FullName -Recurse -Force -File -EA SilentlyContinue | Measure-Object Length -Sum).Sum
    '{0,8:N0} MB  {1}' -f ($s/1MB), $_.FullName
  }

The pub cache is in Local AppData on Windows rather than a dotfolder in the home directory, which is why the paths in most tutorials do not match.

Engine artefacts per platform

Get-ChildItem "$env:USERPROFILE\flutter\bin\cache\artifacts" -Directory -EA SilentlyContinue |
  ForEach-Object {
    $s = (Get-ChildItem $_.FullName -Recurse -Force -File -EA SilentlyContinue | Measure-Object Length -Sum).Sum
    [PSCustomObject]@{ MB = [math]::Round($s/1MB); Name = $_.Name }
  } | Sort-Object MB -Descending

The SDK downloads prebuilt engine binaries for every platform it has been asked about. On a Windows machine targeting Android, web and Windows desktop, that is three sets, and flutter precache with specific platform flags is the supported way to end up with fewer.

Build output across projects

Get-ChildItem $env:USERPROFILE -Recurse -Directory -Include build,.dart_tool -Depth 5 -EA SilentlyContinue |
  Where-Object { Test-Path (Join-Path $_.FullName '..\pubspec.yaml') } |
  Select-Object FullName -First 20

The check for a pubspec.yaml alongside is what distinguishes a Flutter build folder from every other folder called build. Both are regenerated by the next build.

The Android side

A Flutter machine targeting Android also carries the SDK, system images and Gradle caches, which are usually larger than Flutter itself. Those are in Android Studio on Windows.