diff --git a/TESTING_DEV13.md b/TESTING_DEV13.md
new file mode 100644
index 0000000..f27bd10
--- /dev/null
+++ b/TESTING_DEV13.md
@@ -0,0 +1,390 @@
+# VideoTools v0.1.0-dev13 Testing Guide
+
+This document provides a comprehensive testing checklist for all dev13 features.
+
+## Build Status
+- ✅ **Compiles successfully** with no errors
+- ✅ **CLI help** displays correctly with compare command
+- ✅ **All imports** resolved correctly (regexp added for cropdetect)
+
+## Features to Test
+
+### 1. Compare Module
+
+**Test Steps:**
+1. Launch VideoTools GUI
+2. Click "Compare" module button (pink/magenta color)
+3. Click "Load File 1" and select a video
+4. Click "Load File 2" and select another video
+5. Click "COMPARE" button
+
+**Expected Results:**
+- File 1 and File 2 metadata displayed side-by-side
+- Shows: Format, Resolution, Duration, Codecs, Bitrates, Frame Rate
+- Shows: Pixel Format, Aspect Ratio, Color Space, Color Range
+- Shows: GOP Size, Field Order, Chapters, Metadata flags
+- formatBitrate() displays bitrates in human-readable format (Mbps/kbps)
+
+**CLI Test:**
+```bash
+./VideoTools compare video1.mp4 video2.mp4
+```
+
+**Code Verification:**
+- ✅ buildCompareView() function implemented (main.go:4916)
+- ✅ HandleCompare() handler registered (main.go:59)
+- ✅ Module button added to grid with pink color (main.go:69)
+- ✅ formatBitrate() helper function (main.go:4900)
+- ✅ compareFile1/compareFile2 added to appState (main.go:197-198)
+
+---
+
+### 2. Target File Size Encoding Mode
+
+**Test Steps:**
+1. Load a video in Convert module
+2. Switch to Advanced mode
+3. Set Bitrate Mode to "Target Size"
+4. Enter target size (e.g., "25MB", "100MB", "8MB")
+5. Start conversion or add to queue
+
+**Expected Results:**
+- FFmpeg calculates video bitrate from: target size, duration, audio bitrate
+- Reserves 3% for container overhead
+- Minimum 100 kbps sanity check applied
+- Works in both direct convert and queue jobs
+
+**Test Cases:**
+- Video: 1 minute, Target: 25MB, Audio: 192k → Video bitrate calculated
+- Video: 5 minutes, Target: 100MB, Audio: 192k → Video bitrate calculated
+- Very small target that would be impossible → Falls back to 100 kbps minimum
+
+**Code Verification:**
+- ✅ TargetFileSize field added to convertConfig (main.go:125)
+- ✅ Target Size UI entry with placeholder (main.go:1931-1936)
+- ✅ ParseFileSize() parses KB/MB/GB (internal/convert/types.go:205)
+- ✅ CalculateBitrateForTargetSize() with overhead calc (internal/convert/types.go:173)
+- ✅ Applied in startConvert() (main.go:3993)
+- ✅ Applied in executeConvertJob() (main.go:1109)
+- ✅ Passed to queue config (main.go:611)
+
+---
+
+### 3. Automatic Black Bar Detection & Cropping
+
+**Test Steps:**
+1. Load a video with black bars (letterbox/pillarbox)
+2. Switch to Advanced mode
+3. Scroll to AUTO-CROP section
+4. Click "Detect Crop" button
+5. Wait for detection (button shows "Detecting...")
+6. Review detection dialog showing savings estimate
+7. Click "Apply" to use detected values
+8. Verify AutoCrop checkbox is checked
+
+**Expected Results:**
+- Samples 10 seconds from middle of video
+- Uses FFmpeg cropdetect filter (threshold 24)
+- Shows original vs cropped dimensions
+- Calculates and displays pixel reduction percentage
+- Applies crop values to config
+- Works for both direct convert and queue jobs
+
+**Test Cases:**
+- Video with letterbox bars (top/bottom) → Detects and crops
+- Video with pillarbox bars (left/right) → Detects and crops
+- Video with no black bars → Shows "already fully cropped" message
+- Very short video (<10 seconds) → Still attempts detection
+
+**Code Verification:**
+- ✅ detectCrop() function with 30s timeout (main.go:4841)
+- ✅ CropValues struct (main.go:4832)
+- ✅ Regex parsing: crop=(\d+):(\d+):(\d+):(\d+) (main.go:4870)
+- ✅ AutoCrop checkbox in UI (main.go:1765)
+- ✅ Detect Crop button with background execution (main.go:1771)
+- ✅ Confirmation dialog with savings calculation (main.go:1797)
+- ✅ Crop filter applied before scaling (main.go:3996)
+- ✅ Works in queue jobs (main.go:1023)
+- ✅ CropWidth/Height/X/Y fields added (main.go:136-139)
+- ✅ Passed to queue config (main.go:621-625)
+
+---
+
+### 4. Frame Rate Conversion UI with Size Estimates
+
+**Test Steps:**
+1. Load a 60fps video in Convert module
+2. Switch to Advanced mode
+3. Find "Frame Rate" dropdown
+4. Select "30" fps
+5. Observe hint message below dropdown
+
+**Expected Results:**
+- Shows: "Converting 60 → 30 fps: ~50% smaller file"
+- Hint updates dynamically when selection changes
+- Warning shown for upscaling: "⚠ Upscaling from 30 to 60 fps (may cause judder)"
+- No hint when "Source" selected or target equals source
+
+**Test Cases:**
+- 60fps → 30fps: Shows ~50% reduction
+- 60fps → 24fps: Shows ~60% reduction
+- 30fps → 60fps: Shows upscaling warning
+- 30fps → 30fps: No hint (same as source)
+- Video with unknown fps: No hint shown
+
+**Frame Rate Options:**
+- Source, 23.976, 24, 25, 29.97, 30, 50, 59.94, 60
+
+**Code Verification:**
+- ✅ All frame rate options added (main.go:2107)
+- ✅ updateFrameRateHint() function (main.go:2051)
+- ✅ Calculates reduction percentage (main.go:2094-2098)
+- ✅ Upscaling warning (main.go:2099-2101)
+- ✅ frameRateHint label in UI (main.go:2215)
+- ✅ Updates on selection change (main.go:2110)
+- ✅ FFmpeg fps filter already applied (main.go:4643-4646)
+
+---
+
+### 5. Encoder Preset Descriptions
+
+**Test Steps:**
+1. Load any video in Convert module
+2. Switch to Advanced mode
+3. Find "Encoder Preset" dropdown
+4. Select different presets and observe hint
+
+**Expected Results:**
+- Each preset shows speed vs quality trade-off
+- Visual icons: ⚡⏩⚖️🎯🐌
+- Shows percentage differences vs baseline
+- Recommends "slow" as best quality/size ratio
+
+**Preset Information:**
+- ultrafast: ⚡ ~10x faster than slow, ~30% larger
+- superfast: ⚡ ~7x faster than slow, ~20% larger
+- veryfast: ⚡ ~5x faster than slow, ~15% larger
+- faster: ⏩ ~3x faster than slow, ~10% larger
+- fast: ⏩ ~2x faster than slow, ~5% larger
+- medium: ⚖️ Balanced (default baseline)
+- slow: 🎯 Best ratio ~2x slower, ~5-10% smaller (RECOMMENDED)
+- slower: 🎯 ~3x slower, ~10-15% smaller
+- veryslow: 🐌 ~5x slower, ~15-20% smaller
+
+**Code Verification:**
+- ✅ updateEncoderPresetHint() function (main.go:2006)
+- ✅ All 9 presets with descriptions (main.go:2009-2027)
+- ✅ Visual icons for categories (main.go:2010, 2016, 2020, 2022, 2026)
+- ✅ encoderPresetHint label in UI (main.go:2233)
+- ✅ Updates on selection change (main.go:2036)
+- ✅ Initialized with current preset (main.go:2039)
+
+---
+
+## Integration Testing
+
+### Queue System Integration
+**All features must work when added to queue:**
+- [ ] Compare module (N/A - not a conversion operation)
+- [ ] Target File Size mode in queue job
+- [ ] Auto-crop in queue job
+- [ ] Frame rate conversion in queue job
+- [ ] Encoder preset in queue job
+
+**Code Verification:**
+- ✅ All config fields passed to queue (main.go:599-634)
+- ✅ executeConvertJob() handles all new fields
+- ✅ Target Size: lines 1109-1133
+- ✅ Auto-crop: lines 1023-1048
+- ✅ Frame rate: line 1091-1094
+- ✅ Encoder preset: already handled via encoderPreset field
+
+### Settings Persistence
+**Settings should persist across video loads:**
+- [ ] Auto-crop checkbox state persists
+- [ ] Frame rate selection persists
+- [ ] Encoder preset selection persists
+- [ ] Target file size value persists
+
+**Code Verification:**
+- ✅ All settings stored in state.convert
+- ✅ Settings not reset when loading new video
+- ✅ Reset button available to restore defaults (main.go:1823)
+
+---
+
+## Known Limitations
+
+1. **Auto-crop detection:**
+   - Samples only 10 seconds (may miss variable content)
+   - 30-second timeout for very slow systems
+   - Assumes black bars are consistent throughout video
+
+2. **Frame rate conversion:**
+   - Estimates are approximate (actual savings depend on content)
+   - No motion interpolation (drops/duplicates frames only)
+
+3. **Target file size:**
+   - Estimate based on single-pass encoding
+   - Container overhead assumed at 3%
+   - Actual file size may vary by ±5%
+
+4. **Encoder presets:**
+   - Speed/size estimates are averages
+   - Actual performance depends on video complexity
+   - GPU acceleration may alter speed ratios
+
+---
+
+## Manual Testing Checklist
+
+### Pre-Testing Setup
+- [ ] Have test videos ready:
+  - [ ] 60fps video for frame rate testing
+  - [ ] Video with black bars for crop detection
+  - [ ] Short video (< 1 min) for quick testing
+  - [ ] Long video (> 5 min) for queue testing
+
+### Compare Module
+- [ ] Load two different videos
+- [ ] Compare button shows both metadata
+- [ ] Bitrates display correctly (Mbps/kbps)
+- [ ] All fields populated correctly
+- [ ] "Back to Menu" returns to main menu
+
+### Target File Size
+- [ ] Set target of 25MB on 1-minute video
+- [ ] Verify conversion completes
+- [ ] Check output file size (should be close to 25MB ±5%)
+- [ ] Test with very small target (e.g., 1MB)
+- [ ] Verify in queue job
+
+### Auto-Crop
+- [ ] Detect crop on letterbox video
+- [ ] Verify savings percentage shown
+- [ ] Apply detected values
+- [ ] Convert with crop applied
+- [ ] Compare output dimensions
+- [ ] Test with no-black-bar video (should say "already fully cropped")
+- [ ] Verify in queue job
+
+### Frame Rate Conversion
+- [ ] Load 60fps video
+- [ ] Select 30fps
+- [ ] Verify hint shows "~50% smaller"
+- [ ] Select 60fps (same as source)
+- [ ] Verify no hint shown
+- [ ] Select 24fps
+- [ ] Verify different percentage shown
+- [ ] Try upscaling (30→60)
+- [ ] Verify warning shown
+
+### Encoder Presets
+- [ ] Select "ultrafast" - verify hint shows
+- [ ] Select "medium" - verify balanced description
+- [ ] Select "slow" - verify recommendation shown
+- [ ] Select "veryslow" - verify maximum compression note
+- [ ] Test actual encoding with different presets
+- [ ] Verify speed differences are noticeable
+
+### Error Cases
+- [ ] Auto-crop with no video loaded → Should show error dialog
+- [ ] Very short video for crop detection → Should still attempt
+- [ ] Invalid target file size (e.g., "abc") → Should handle gracefully
+- [ ] Extremely small target size → Should apply 100kbps minimum
+
+---
+
+## Performance Testing
+
+### Auto-Crop Detection Speed
+- Expected: ~2-5 seconds for typical video
+- Timeout: 30 seconds maximum
+- [ ] Test on 1080p video
+- [ ] Test on 4K video
+- [ ] Test on very long video (should still sample 10s)
+
+### Memory Usage
+- [ ] Load multiple videos in compare mode
+- [ ] Check memory doesn't leak
+- [ ] Test with large (4K+) videos
+
+---
+
+## Regression Testing
+
+Verify existing features still work:
+- [ ] Basic video conversion works
+- [ ] Queue add/remove/execute works
+- [ ] Direct convert (not queued) works
+- [ ] Simple mode still functional
+- [ ] Advanced mode shows all controls
+- [ ] Aspect ratio handling works
+- [ ] Deinterlacing works
+- [ ] Audio settings work
+- [ ] Hardware acceleration detection works
+
+---
+
+## Documentation Review
+
+- ✅ DONE.md updated with all features
+- ✅ TODO.md marked features as complete
+- ✅ Commit messages are descriptive
+- ✅ Code comments explain complex logic
+- [ ] README.md updated (if needed)
+
+---
+
+## Code Quality
+
+### Code Review Completed:
+- ✅ No compilation errors
+- ✅ All imports resolved
+- ✅ No obvious logic errors
+- ✅ Error handling present (dialogs, nil checks)
+- ✅ Logging added for debugging
+- ✅ Function names are descriptive
+- ✅ Code follows existing patterns
+
+### Potential Issues to Watch:
+- Crop detection regex assumes specific FFmpeg output format
+- Frame rate hint calculations assume source FPS is accurate
+- Target size calculation assumes consistent bitrate encoding
+- 30-second timeout for crop detection might be too short on very slow systems
+
+---
+
+## Sign-off
+
+**Build Status:** ✅ PASSING
+**Code Review:** ✅ COMPLETED
+**Manual Testing:** ⏳ PENDING (requires video files)
+**Documentation:** ✅ COMPLETED
+
+**Ready for User Testing:** YES (with video files)
+
+---
+
+## Testing Commands
+
+```bash
+# Build
+go build -o VideoTools
+
+# CLI Help
+./VideoTools help
+
+# Compare (CLI)
+./VideoTools compare video1.mp4 video2.mp4
+
+# GUI
+./VideoTools
+
+# Debug mode
+VIDEOTOOLS_DEBUG=1 ./VideoTools
+```
+
+---
+
+Last Updated: 2025-12-03