How to Use ResEdit to Modify App Icons and Resources

7 Advanced ResEdit Techniques Every Power User Should Know

1. Edit and create custom resource templates (TMPL)

• Open an application’s resource fork and add or modify TMPL resources to define new structured resource types.
• Use TMPL to create custom editors for complex resources (e.g., custom UI components) so ResEdit shows a friendly form instead of raw hex.

2. Patch dialog layouts and behavior (DLOG / ALRT)

• Modify DLOG and ALRT resources to change dialog text, button order, and default button IDs.
• Adjust control positions and sizes so altered dialogs remain usable across different localizations.

3. Replace and rebuild icons and cursors (ICN#, CURS, ‘ICON’)

• Edit 32×32 and 16×16 icon/cursor bitmaps directly in ResEdit’s built-in editor or paste edited bitmaps from a raster editor.
• Update multiple icon resources (ICN#, ‘ICON’) and ensure proper resource IDs and masks are kept in sync.

4. Create or modify keyboard layouts (KCHR)

• Add new KCHR resources to implement custom keyboard mappings or extended symbols (e.g., currency, special punctuation).
• Test by assigning the KCHR resource ID as active for the system or app; include modifier mappings for Shift/Option/Cmd.

5. Inject code fragments and patch resource-based code (CODE, INIT)

• For Classic Mac apps, carefully edit CODE and INIT resources to patch small 68K routines or change initialization behavior.
• Always work on backups and verify checksum/length fields; use disassembly tools to understand patched offsets.

6. Localize apps by editing STR# and ‘cfrg’/‘TEXT’ resources

• Edit STR# string lists and language-specific TEXT resources to produce accurate translations without recompiling.
• Keep message length and formatting constraints in mind (padding, null terminators) and test in-app for truncation.

7. Maintain creator/type and file metadata safely

• Use ResEdit to change file type/creator codes and add custom resources that apps will detect as plugins or themes.
• When modifying bundles or files on modern macOS, extract and reattach resource forks correctly (e.g., via ._AppleDouble files or HFS+ tools) to avoid data loss.

Tips for safety and compatibility

• Always work on copies and keep original