UUIDジェネレーター
ランダムなUUID/GUID識別子を生成
5 × 36 chars
次に進む
関連する次のアクションでワークフローを続けます。
数量
5
大文字
Off
ハイフンなし
Off
結果
まだ結果はありません
Privacy & Trust
生成
Generation uses `crypto.randomUUID()` for standards-aligned UUID v4 output.
ハイフンなし
Compact mode is useful when identifiers need to fit into filenames, URLs, or constrained fields.
結果
Everything is created locally in the browser, so temporary identifiers never need a server round-trip.
生成されたUUID
Generate at least one UUID to enable export.
使い方
値を入力
入力フィールドに数値やパラメータを入力します。
即座に結果を取得
入力するとすぐに結果が更新されます — 送信ボタンは不要です。
コピーまたは保存
結果をクリップボードにコピーするか、ワークフローで活用します。
このツールを使う理由
完全無料
Core tools are free. AI and cloud tools may have daily usage limits.
インストール不要
すべてブラウザで実行されます。ソフトウェアのダウンロードやインストールは不要です。
プライベート＆安全
Local tools keep input on your device. Tools that transmit data are clearly labelled.
モバイル対応
完全レスポンシブ対応 — スマートフォン、タブレット、デスクトップで利用できます。
UUIDs: Universally Unique Identifiers Explained
Key Takeaways
- UUIDs (v4) use 122 bits of randomness to generate identifiers that are statistically guaranteed to be unique across all systems worldwide.
- UUID v4 is the most common version — purely random with no embedded timestamp or machine information.
- All UUIDs are generated in your browser using cryptographic randomness — nothing is stored or transmitted.
Universally Unique Identifiers (UUIDs) solve the fundamental distributed systems problem of generating unique identifiers without central coordination. Whether you are building microservices, designing database schemas, or creating distributed systems, UUIDs provide a standardized way to create identifiers that will never collide, even across independent systems.
1 in 5.3 × 10^36
UUID v4 collision probability
Key Concepts
UUID Versions
UUID v1 uses timestamp + MAC address. V3 uses MD5 namespace hashing. V4 uses pure randomness. V5 uses SHA-1 namespace hashing. V7 (new) combines timestamp with randomness for sortability.
UUID v4 Structure
A UUID v4 follows the format xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx where '4' indicates version 4 and 'y' is constrained to 8, 9, a, or b to indicate the variant. The remaining 122 bits are random.
UUID vs. Auto-Increment IDs
Auto-increment IDs are sequential and predictable, leaking information about record count and creation order. UUIDs are random and reveal nothing, making them better for public-facing identifiers.
UUID v7 — The New Standard
UUID v7 (RFC 9562) embeds a Unix timestamp in the first 48 bits, making UUIDs naturally sortable by creation time while maintaining randomness. This is ideal for database primary keys.
Pro Tips
Use UUID v7 for database primary keys — the embedded timestamp makes them naturally sortable, improving B-tree index performance.
Store UUIDs as binary (16 bytes) in databases rather than as strings (36 characters) for significant storage and performance gains.
Remove hyphens when UUIDs are used in URLs to keep them compact while maintaining readability.
Use crypto.randomUUID() in modern browsers — it is faster and more secure than JavaScript UUID libraries.
All UUIDs are generated entirely in your browser using the Web Crypto API. No generated identifiers are stored, logged, or transmitted to any server.