A Developer’s Guide to Inspecting and Editing PList FilesProperty List files (commonly called plist files) are a foundational configuration and data format used across Apple platforms — macOS, iOS, iPadOS, tvOS and watchOS. They store structured data such as app settings, configuration, serialized objects, and localized information. For developers working in the Apple ecosystem, being able to inspect, interpret, and edit plist files safely and efficiently is essential. This guide covers the formats, tools, common workflows, best practices, and troubleshooting tips for working with plist files.
What is a plist?
A plist (property list) is a structured data representation used by Apple frameworks to store small to medium-sized amounts of data. A plist can represent standard data types including:
- strings
- numbers (integers and floating point)
- booleans
- dates
- data blobs (binary)
- arrays
- dictionaries (key-value maps)
Plists can be encoded in two main formats:
- XML — human-readable, editable in a text editor, verbose.
- Binary — compact, faster to parse, not human-readable without a tool.
Since macOS 10.0, property lists have been an official serialization format used by Cocoa and Foundation via NSDictionary, NSArray, NSUserDefaults, and PropertyListSerialization.
Why developers need to read and edit plists
Common use cases:
- Inspecting app bundles (Info.plist) to check bundle identifiers, versioning, URL schemes, exported entitlements, and capabilities.
- Debugging configuration issues where settings are stored in plists (preferences, launch services, entitlements caches).
- Migrating, merging, or transforming app configuration between environments.
- Editing test/sample data for apps that load plist-based fixtures.
- Reverse engineering or security auditing of macOS/iOS apps.
Tools for inspecting and editing plist files
Below are common tools and their typical uses.
- Xcode’s Property List editor (GUI)
- Best for developers using Xcode; opens Info.plist and other plists in a structured, form-like view.
- macOS TextEdit or any text editor
- Works for XML plists; not useful for binary plists.
- plutil (command-line, macOS)
- Converts between XML and binary, validates format, prints human-readable output.
- Examples:
- Validate: plutil -lint file.plist
- Convert to XML: plutil -convert xml1 file.plist
- Convert to binary: plutil -convert binary1 file.plist
- defaults (command-line, macOS)
- Reads and writes user defaults (preference plists) in the correct domain.
- Example: defaults read com.example.app
- pbxproj / git diff tools
- When plists are XML, standard diffs work; for binary plists, convert to XML before diffing.
- Property List Editor (standalone tools / third-party)
- Several third-party GUI apps provide advanced editing, searching, and batch operations.
- Python / Swift / Objective-C scripts
- Programmatic manipulation using Foundation’s PropertyListSerialization (Apple platforms) or Python’s plistlib.
- Example Python snippet:
import plistlib with open("example.plist", "rb") as f: data = plistlib.load(f) data["NewKey"] = "value" with open("example.plist", "wb") as f: plistlib.dump(data, f)
Inspecting plists safely
-
Identify the format
- Use plutil -p file.plist to print a human-readable tree (works for both formats).
- Use file file.plist to see if it is binary or XML.
-
Back up before changing
- Always make a copy: cp file.plist file.plist.bak
- If file is in a Git repo, commit before editing to keep a clean history.
-
Use read-only tools first
- Start with plutil -p or defaults read to inspect values without modifying the file.
-
Be cautious with Info.plist and entitlements
- Changes to Info.plist (bundle metadata) can break code signing, App Store submission, or runtime behavior.
- Entitlements are tied to code signing; editing entitlements or matching them to provisioning profiles must be done carefully.
Editing plists: approaches and examples
Method 1 — Xcode plist editor (GUI)
- Double-click an XML plist in Finder or open it within Xcode.
- Use the structured key/value table to add or remove keys; Xcode preserves types (String, Number, Boolean, Date, Data, Array, Dictionary).
Method 2 — plutil for conversion + text editor
- Convert binary to XML:
- plutil -convert xml1 file.plist
- Edit in your text editor (respect XML structure and types).
- Convert back to binary if needed:
- plutil -convert binary1 file.plist
Method 3 — defaults for preference domains
- Read domain: defaults read com.example.app
- Write value: defaults write com.example.app SomeKey -string “value”
- Note: defaults operates on the user’s preferences database and may cache values — sometimes a logout/login or killing related processes is required.
Method 4 — Programmatic editing (Python example)
- Use the earlier plistlib snippet to load, modify, and save. This is ideal for batch edits or transformations.
Method 5 — Swift / Objective-C
- Swift example using PropertyListSerialization or PropertyListDecoder/Encoder for typed models.
Practical examples
- Convert a binary plist to readable XML and print key “CFBundleIdentifier”:
- Convert: plutil -convert xml1 MyApp.app/Contents/Info.plist
- Print key: /usr/libexec/PlistBuddy -c “Print :CFBundleIdentifier” MyApp.app/Contents/Info.plist (PlistBuddy is another helpful macOS utility for structured reads/writes.)
- Merge two plist dictionaries programmatically (Python): “`python import plistlib from collections import ChainMap
with open(“a.plist”, “rb”) as fa, open(“b.plist”, “rb”) as fb:
A = plistlib.load(fa) B = plistlib.load(fb)
B overrides A
merged = dict(ChainMap(B, A))
with open(“merged.plist”, “wb”) as fm:
plistlib.dump(merged, fm)
”`
Best practices
- Prefer XML during development for easier diffs and reviews; convert to binary for shipping if size or speed matters.
- Keep plists in source control as XML. If third-party tools produce binary plists, convert them before committing.
- Validate after edits: plutil -lint file.plist
- Use typed editors (Xcode/PlistBuddy) rather than raw text edits when possible, to avoid type mismatches (e.g., numeric vs string).
- Avoid storing large blobs in plists; use separate files or a proper database for larger data.
- When modifying system or app preference plists, be aware of caching — changes may not take effect until the app reads them again or the system refreshes.
Troubleshooting common issues
- “App crashes after Info.plist edit” — likely malformed XML, wrong type, or missing required keys. Validate with plutil -lint and check code signing.
- “Defaults not taking effect” — user defaults are cached. Try killing the app, rebooting, or using defaults read/write properly. For sandboxed apps, ensure the correct container/domain is targeted.
- “Binary plists appear unreadable” — convert to XML with plutil -convert xml1, then inspect.
- “Merge conflicts on Info.plist” — convert to XML, resolve conflicts manually, ensure types remain correct, and run plutil -lint before committing.
Security and privacy considerations
- Plists can contain sensitive information (API keys, tokens, user identifiers). Don’t commit secrets to source control.
- On iOS, preference files in user containers can be accessed only by the app (sandboxed), but shared or exported plists can reveal sensitive state — handle them carefully.
- When distributing apps, ensure no debug data or leftover configuration containing secrets remains in Info.plist or embedded plists.
Advanced tips
- Use PlistBuddy for fine-grained edits:
- Print a value: /usr/libexec/PlistBuddy -c “Print :Root:Key” file.plist
- Set a value: /usr/libexec/PlistBuddy -c “Set :Root:Key value” file.plist
- For reproducible builds, script plist modifications (Python, Swift) in your build pipeline.
- Use PropertyListEncoder/Decoder with Codable in Swift to map plists to typed models for safer parsing and editing.
- When analyzing iOS backups, many app settings and data appear as plists; tools that parse backups will often convert those into readable forms.
Summary
Understanding plist structure, available tools, and safe editing workflows lets you inspect and modify app configuration reliably. Use XML during development for visibility, validate all changes, and prefer programmatic edits when automating or performing batch transformations. Careful handling of Info.plist, entitlements, and preference files prevents runtime issues and keeps apps secure.