Generate UUID in Dart

UUID v4 - Random (recommended default)

import 'package:uuid/uuid.dart';

const uuid = Uuid();
final id = uuid.v4();
print(id); // → "550e8400-e29b-41d4-a716-446655440000"

UUID v7 - Time-ordered (database PKs)

import 'package:uuid/uuid.dart';

const uuid = Uuid();

// Millisecond-precision timestamp prefix - sorts chronologically
final id = uuid.v7();
print(id); // → "018e8f6a-1b2c-7d3e-9f4a-5b6c7d8e9f0a"

UUID v5 - Deterministic / Namespace-based

import 'package:uuid/uuid.dart';

const uuid = Uuid();

// SHA-1 hash of namespace + name - same inputs always produce the same UUID
final id = uuid.v5(Uuid.NAMESPACE_DNS, 'example.com');
print(id); // → always "cfbff0d1-9375-5685-968c-48ce8b15ae17"

1. Dart model class with UUID primary key

import 'package:uuid/uuid.dart';

const _uuid = Uuid();

class Order {
  final String id;
  final String customerName;
  final double total;
  final DateTime createdAt;

  Order({
    String? id,
    required this.customerName,
    required this.total,
  })  : id = id ?? _uuid.v4(),
        createdAt = DateTime.now();

  Map<String, dynamic> toJson() => {
    'id': id,
    'customerName': customerName,
    'total': total,
    'createdAt': createdAt.toIso8601String(),
  };
}

2. Shelf server - request tracing middleware

import 'package:shelf/shelf.dart';
import 'package:uuid/uuid.dart';

const _uuid = Uuid();

Middleware requestIdMiddleware() {
  return (Handler innerHandler) {
    return (Request request) async {
      final requestId = _uuid.v4();
      final updatedRequest = request.change(
        headers: {...request.headers, 'x-request-id': requestId},
      );
      final response = await innerHandler(updatedRequest);
      return response.change(
        headers: {...response.headers, 'x-request-id': requestId},
      );
    };
  };
}

3. Idempotent API call with UUID key

import 'dart:convert';
import 'package:http/http.dart' as http;
import 'package:uuid/uuid.dart';

const _uuid = Uuid();

Future<Map<String, dynamic>> createPayment({
  required String customerId,
  required int amountCents,
}) async {
  final idempotencyKey = _uuid.v4();

  final response = await http.post(
    Uri.parse('https://api.example.com/payments'),
    headers: {
      'Content-Type': 'application/json',
      'Idempotency-Key': idempotencyKey,
    },
    body: jsonEncode({'customerId': customerId, 'amount': amountCents}),
  );

  return jsonDecode(response.body) as Map<String, dynamic>;
}

How do I generate a UUID in Dart?

The uuid package on pub.dev is the standard choice for Dart and Flutter. Add uuid to pubspec.yaml, create const uuid = Uuid(), and call uuid.v4() for a random UUID or uuid.v7() for a time-ordered one. It uses a cryptographically secure RNG by default.

Is Uuid().v4() cryptographically secure?

Yes. Uuid().v4() uses the platform CSPRNG (operating system secure random source), suitable for session tokens, API keys, and idempotency keys. Do not use non-cryptographic random sources for security-sensitive identifiers.

What is the difference between UUID v4 and v7 in Dart?

UUID v4 (Uuid().v4() or equivalent) is fully random and not sortable. UUID v7 embeds a millisecond timestamp for chronological sorting (RFC 9562). Use v4 for general-purpose IDs; use v7 for database primary keys at scale.

Do I need to install a package for UUID generation in Dart?

A package or library install may be required. See the Installation section for the recommended approach in Dart.

How do I validate a UUID string in Dart?

Use the platform's UUID parse/validation function, or test against the RFC 4122 regex: /^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i. Always validate external input at API boundaries.

Should I use UUIDs as database primary keys in Dart applications?

UUIDs work well as primary keys for distributed systems. Prefer native UUID/BINARY(16) column types over VARCHAR(36). For very large tables, consider UUID v7 for better B-tree insert locality.

Can I generate UUIDs in Dart without a network connection?

Yes. UUID generation uses local OS entropy sources and does not require network access. Each call is independent and thread-safe on modern platforms.

What output formats are available in Dart?

The standard hyphenated lowercase string (36 chars) is the default. Most APIs also support 32-char hex (no hyphens) and 16-byte binary formats. Use string format for APIs and binary for database storage.

What RFC standards apply to Dart UUID generation?

Version 4 UUIDs follow RFC 4122. UUID v7 follows RFC 9562 (May 2024). Ensure your chosen method produces compliant version and variant bits.

When should I avoid UUID v1?

Avoid UUID v1 in security-sensitive contexts - it embeds MAC address and timestamp information. Prefer v4 (Uuid().v4() or equivalent) unless you need legacy Cassandra timeuuid compatibility.