Built-in libraries in Dart provide additional functionalities beyond the core language features. They offer various utilities and tools for common programming tasks. Here are some of the most commonly used built-in libraries in Dart:

1. dart:core

• Provides fundamental classes and utilities that are automatically imported into every Dart program.
• Examples: int, double, String, List, Map, print(), etc.

2. dart:io

• Provides classes and functions for working with files, directories, and other input/output operations.
• Examples: File, Directory, stdin, stdout, stderr, etc.

3. dart:async

• Provides classes and utilities for asynchronous programming, including futures, streams, and timers.
• Examples: Future, Stream, Timer, etc.

4. dart:convert

• Provides classes for converting between different data formats, such as JSON, UTF-8, and base64.
• Examples: jsonEncode(), jsonDecode(), utf8.encode(), utf8.decode(), etc.

5. dart:math

• Provides mathematical functions and constants for performing mathematical operations.
• Examples: sqrt(), sin(), cos(), max(), min(), etc.

6. dart:collection

• Provides specialized collection classes beyond the built-in List and Map, such as Queue, HashSet, LinkedHashMap, etc.

7. dart:html