diff --git a/Sources/GrowthLapse/ContentView.swift b/Sources/GrowthLapse/ContentView.swift
index bf80cd1..8690831 100644
--- a/Sources/GrowthLapse/ContentView.swift
+++ b/Sources/GrowthLapse/ContentView.swift
@@ -253,6 +253,9 @@ struct ContentView: View {
                 selectedClipID = project?.clips.first?.id
             }
         }
+        .onChange(of: settings.sortMode) { sortMode in
+            processor.reorderProject(sortMode: sortMode)
+        }
     }
 
     private var statusHeader: some View {
@@ -307,7 +310,8 @@ struct ContentView: View {
     }
 
     private func projectReviewPanel(_ project: GrowthLapseProject) -> some View {
-        let selectedClip = project.clips.first { $0.id == selectedClipID } ?? project.clips.first
+        let orderedClips = orderedProjectClips(project.clips)
+        let selectedClip = orderedClips.first { $0.id == selectedClipID } ?? orderedClips.first
 
         return VStack(alignment: .leading, spacing: 10) {
             HStack {
@@ -328,7 +332,7 @@ struct ContentView: View {
             }
 
             HStack(alignment: .top, spacing: 12) {
-                List(project.clips, selection: $selectedClipID) { clip in
+                List(orderedClips, selection: $selectedClipID) { clip in
                     VStack(alignment: .leading, spacing: 2) {
                         HStack {
                             Text(String(format: "%03d", clip.index))
@@ -429,6 +433,28 @@ struct ContentView: View {
         processor.project?.clips.first { $0.id == id }
     }
 
+    private func orderedProjectClips(_ clips: [GrowthLapseProjectClip]) -> [GrowthLapseProjectClip] {
+        clips.sorted { left, right in
+            switch settings.sortMode {
+            case .filenameAscending:
+                return left.displayName.localizedStandardCompare(right.displayName) == .orderedAscending
+            case .ageWeeksAscending:
+                if left.ageWeeks != right.ageWeeks {
+                    return (left.ageWeeks ?? Int.max) < (right.ageWeeks ?? Int.max)
+                }
+                return left.displayName.localizedStandardCompare(right.displayName) == .orderedAscending
+            case .modificationDateAscending:
+                return left.index < right.index
+            }
+        }
+        .enumerated()
+        .map { offset, clip in
+            var updated = clip
+            updated.index = offset + 1
+            return updated
+        }
+    }
+
     private var errorBinding: Binding<Bool> {
         Binding(
             get: {
diff --git a/Sources/GrowthLapse/VideoProcessor.swift b/Sources/GrowthLapse/VideoProcessor.swift
index d9b6eb9..dde525a 100644
--- a/Sources/GrowthLapse/VideoProcessor.swift
+++ b/Sources/GrowthLapse/VideoProcessor.swift
@@ -69,7 +69,7 @@ final class VideoProcessor: ObservableObject {
         state = .running
 
         let settingsCopy = settings
-        let projectCopy = project
+        let projectCopy = reorderedProject(project, sortMode: settings.sortMode)
         renderTask = Task {
             do {
                 let outcome = try await render(settings: settingsCopy, existingProject: projectCopy)
@@ -106,6 +106,15 @@ final class VideoProcessor: ObservableObject {
         saveProject(project)
     }
 
+    func reorderProject(sortMode: SortMode) {
+        guard let project else {
+            return
+        }
+        let reordered = reorderedProject(project, sortMode: sortMode)
+        self.project = reordered
+        saveProject(reordered)
+    }
+
     func confirmProjectAndDeleteCache() {
         guard let project else {
             return
@@ -1039,6 +1048,41 @@ final class VideoProcessor: ObservableObject {
         )
     }
 
+    private func reorderedProject(_ project: GrowthLapseProject, sortMode: SortMode) -> GrowthLapseProject {
+        var copy = project
+        copy.clips = sortedProjectClips(project.clips, sortMode: sortMode).enumerated().map { offset, clip in
+            var updated = clip
+            updated.index = offset + 1
+            return updated
+        }
+        return copy
+    }
+
+    private func sortedProjectClips(_ clips: [GrowthLapseProjectClip], sortMode: SortMode) -> [GrowthLapseProjectClip] {
+        clips.sorted { left, right in
+            switch sortMode {
+            case .filenameAscending:
+                return left.displayName.localizedStandardCompare(right.displayName) == .orderedAscending
+            case .ageWeeksAscending:
+                if left.ageWeeks != right.ageWeeks {
+                    return (left.ageWeeks ?? Int.max) < (right.ageWeeks ?? Int.max)
+                }
+                return left.displayName.localizedStandardCompare(right.displayName) == .orderedAscending
+            case .modificationDateAscending:
+                let leftDate = modificationDate(for: left.sourceURL)
+                let rightDate = modificationDate(for: right.sourceURL)
+                if leftDate != rightDate {
+                    return leftDate < rightDate
+                }
+                return left.displayName.localizedStandardCompare(right.displayName) == .orderedAscending
+            }
+        }
+    }
+
+    private func modificationDate(for url: URL) -> Date {
+        (try? url.resourceValues(forKeys: [.contentModificationDateKey]).contentModificationDate) ?? .distantPast
+    }
+
     private func saveProject(_ project: GrowthLapseProject) {
         let url = GrowthLapseProject.url(for: project.outputFileURL)
         do {