Strings in Dart

By Syncfusion®, Inc. · Last updated November 11, 2026

How to create strings, put values inside them, compare, search, cut, change, split and join them, build long text with StringBuffer, and handle Unicode and emoji.

What Is a String?

String = a piece of text: letters, digits, spaces, symbols and emoji, in order.

For example:

• a name: 'Asha'
• a sentence: 'Today is Sports Day.'
• digits you never do maths on: '600001'

Each character has a position, starting at 0, just like a list (see Lists).

Simple lesson: a String is text, and Dart gives you many tools to search, cut and change it.

A Real-World Example

The school app shows "Welcome, ASHA!" on the home screen.

• The name comes from the database as ' asha ', with extra spaces.
• The app trims the spaces, makes it upper case, and puts it inside a sentence.

Three string tools, one line of code. Try the tools yourself:

What You Will Learn

In this lesson, you will learn:

1. How to create strings, including multi-line and raw strings.
2. String properties, interpolation, joining and comparing.
3. How to search, extract and change parts of a string.
4. How to change case, trim, split and join.
5. How to build long text with StringBuffer, and handle Unicode and emoji.

String Fundamentals

Creating Strings

Single, double, multi-line and raw

void main() {
  var school = 'Green Valley';
  var quote = "It's Sports Day!";
  var address = '''Green Valley School
12, MG Road
Pune''';
  var path = r'C:\notes\new $file';
  print(school);
  print(quote);
  print(address);
  print(path);
}

Escape sequence = a backslash code for a special character, like \n (new line), \t (tab), \' (a quote) or \$ (a dollar sign).

Simple lesson: use single quotes normally, three quotes for many lines, and r'' to keep backslashes.

String Properties

String properties

void main() {
  var name = 'Asha';
  print(name.length);
  print(name.isEmpty);
  print(''.isEmpty);
  print(name.codeUnits);
  print(name[0]);
  print(name[name.length - 1]);
}

name[0] gives the first character. The last one is at length - 1.

Simple lesson: length counts the characters, and [i] reads one character.

String Interpolation

String interpolation = putting a value inside a string.

• $name = put a variable's value here.
• ${expression} = work out an expression, then put its value here.

$ and ${}

void main() {
  var name = 'Ravi';
  var maths = 88;
  var science = 91;
  print('Hello, $name!');
  print('Total: ${maths + science}');
  print('Name in capitals: ${name.toUpperCase()}');
  print('Price: \$5');
}

• $name.toUpperCase() would NOT work. Dart would put name in, then print .toUpperCase() as text. Use ${...} for anything more than a plain name.
• \$ prints a real dollar sign.

Simple lesson: use $name for a plain variable and ${...} for anything more.

Concatenation

Concatenation = joining strings end to end.

• + joins two strings: 'Green' + ' Valley'.
• Adjacent string literals = two literals written side by side are joined automatically.

Joining strings

void main() {
  var first = 'Green';
  var full = first + ' ' + 'Valley';
  print(full);

  var notice = 'School will close early today '
      'because of the rain.';
  print(notice);

  var marks = 92;
  print('Marks: ' + marks.toString());
}

+ only joins Strings. A number needs toString(), or better, interpolation: 'Marks: $marks'.

Simple lesson: prefer interpolation, use + for short joins, and split long text into adjacent literals.

String Comparison

• == = are the two strings exactly the same? Capital letters matter.
• compareTo() = which comes first in dictionary order? Gives -1, 0 or 1.

Comparing strings

void main() {
  print('Asha' == 'Asha');
  print('Asha' == 'asha');
  print('apple'.compareTo('banana'));
  print('mango'.compareTo('apple'));
  print('kiwi'.compareTo('kiwi'));
  print('asha'.toLowerCase() == 'ASHA'.toLowerCase());
}

To compare without caring about case, change both to lower case first.

Simple lesson: == checks exact equality, and compareTo gives dictionary order.

Searching Strings

Searching inside text

void main() {
  var email = 'asha.k@greenvalley.edu';
  print(email.contains('@'));
  print(email.startsWith('asha'));
  print(email.endsWith('.edu'));
  print(email.indexOf('@'));
  print(email.lastIndexOf('.'));
  print(email.indexOf('#'));
}

Simple lesson: contains, startsWith and endsWith say yes or no, and indexOf says where.

Extracting Text

substring(start, end) = the characters from start up to (not including) end.

Accessing Characters

text[i] gives the character at index i, as a one-letter String.

Simple lesson: substring cuts out a piece by index, and [i] reads one character.

Modifying Strings

Strings never change. These methods give back a new string:

Replacing and padding

void main() {
  var notice = 'Holiday on Monday. Monday is a holiday.';
  print(notice.replaceAll('Monday', 'Friday'));
  print(notice.replaceFirst('Monday', 'Friday'));
  print('9876543210'.replaceRange(2, 8, '******'));
  print('7'.padLeft(3, '0'));
  print('Maths'.padRight(10, '.') + '92');
  print('Science'.padRight(10, '.') + '85');
}

padLeft(3, '0') turns roll number 7 into 007. padRight lines up a report card.

Simple lesson: replaceAll swaps text, and padLeft and padRight make text a fixed width.

Case Conversion and Whitespace

• toUpperCase() / toLowerCase() = all capitals, or all small letters.
• trim() = removes spaces at both ends.
• trimLeft() / trimRight() = only at the left, or only at the right.

Cleaning up a typed name

void main() {
  var typed = '   aSHa   ';
  print('[${typed.trim()}]');
  print('[${typed.trimLeft()}]');
  print('[${typed.trimRight()}]');
  var clean = typed.trim().toLowerCase();
  print(clean);
  print(clean[0].toUpperCase() + clean.substring(1));
}

The brackets show where the spaces are. The last line makes "Asha" with a capital first letter.

Simple lesson: trim() removes extra spaces, and the case methods fix capital letters.

Splitting and Joining

• split(separator) = cuts a string into a List of pieces.
• join(separator) = the opposite, on a list: glues the pieces into one string.

From text to a list, and back

void main() {
  var csv = 'Asha,Ravi,Priya,Kiran';
  var names = csv.split(',');
  print(names);
  print(names.length);
  print(names.join(' | '));
  print('Hello'.split(''));
  var words = 'Dart is fun'.split(' ');
  print(words.reversed.join(' '));
}

split('') cuts between every character.

String Conversion

toString() turns any value into text (see Data Types): 92.toString() gives '92'.

Simple lesson: split turns text into a list, and join turns a list into text.

StringBuffer

StringBuffer Fundamentals

StringBuffer = a tool for building a long string piece by piece.

Joining with + in a loop makes a brand new string every round. A StringBuffer keeps adding to one place, which is faster.

StringBuffer Operations

Building a report card

void main() {
  var marks = {'Maths': 92, 'Science': 85, 'English': 78};
  var report = StringBuffer();
  report.writeln('REPORT CARD');
  report.writeln('-----------');
  marks.forEach((subject, mark) {
    report.write(subject.padRight(10));
    report.writeln(mark);
  });
  report.write('Subjects: ');
  report.writeAll(marks.keys, ', ');
  print(report.toString());
  print('Characters: ${report.length}');
}

Simple lesson: use a StringBuffer to build long text, then call toString() once at the end.

Runes and Unicode

Unicode Characters and Emoji

Unicode = a world-wide list that gives every character a number: A is 65, अ is 2309, 😀 is 128512.

• Dart strings store text as UTF-16 units.
• Most characters use one unit.
• Many emoji use two units, so length counts them as 2.

runes

Rune = one Unicode character code.

Emoji, length and runes

void main() {
  var smile = '😀';
  print(smile.length);
  print(smile.runes.length);
  print(smile.runes.first);
  print('नमस्ते'.length);
  print(String.fromCharCode(65));
  print(String.fromCharCodes([72, 105]));
  print('\u{1F44D} Well done!');
}

• runes counts real characters, so 😀 is 1 rune.
• String.fromCharCode(n) = turns a character code into a string.
• \u{...} = writes a character by its Unicode number.

Simple lesson: length counts UTF-16 units, and runes counts real characters.

TL;DR

1. String = text in quotes. Multi-line: '''...'''. Raw: r'...'.

   • Never changes. Methods give a new string.
2. Interpolation: $name and ${expression}. Join: +, or adjacent literals.

3. Compare: == (exact), compareTo (-1, 0, 1).

   • Search: contains, startsWith, endsWith, indexOf, lastIndexOf.

4. Cut and change: substring, [i], replaceAll, replaceFirst, replaceRange, padLeft, padRight.

   • Clean: toUpperCase, toLowerCase, trim. Split and join: split, join.

5. StringBuffer = write, writeln, writeAll, clear, toString.

   • Unicode: runes, codeUnits, String.fromCharCode, \u{...}.

Common mistakes

Check Yourself

Exercises

What to Remember

• A string is text in quotes. It never changes, so every method gives a new string.
• Use $name and ${expression} to put values inside text.
• contains, indexOf and substring find and cut text.
• replaceAll, trim, toUpperCase, split and join change and reshape text.
• Build long text with StringBuffer, and use runes to count real characters.

Next: Date and Time. You will learn to work with dates, times and durations, like exam days and homework deadlines.