Encodeur/Décodeur Base64

Encodez du texte en Base64 ou decodez du Base64 en texte UTF-8 lisible. Prend en charge le Base64 standard et compatible URL, sans televersement.

Encode and decode Base64 without uploading your data

Full UTF-8 support, URL-safe mode, and real-time conversion — right in your browser. No uploads, no sign-up, no limits.

100% privé

UTF-8 sécurisé

Gratuit pour toujours

Comment l'utiliser

1
Collez votre texte
Saisissez du texte a encoder ou collez une chaine Base64 a decoder.
2
Choisissez le format
Utilisez Base64 standard pour les donnees courantes et le mode compatible URL pour les tokens et query strings.
3
Encodez, decodez ou copiez
Lancez la conversion et copiez le resultat.

Pourquoi utiliser cet outil Base64?

Compatible UTF-8

Traite le texte international sans casser les caracteres.

Mode compatible URL

Adapte les caracteres et le padding pour les usages web.

Dans le navigateur

Pratique pour les extraits, tokens et valeurs de configuration privees.

Understanding Base64 Encoding

What is Base64 and why use it?

Base64 is an encoding scheme that converts binary data into a text representation using 64 ASCII characters (A-Z, a-z, 0-9, +, /). The encoding process takes every 3 bytes of input and converts them into 4 Base64 characters. This ensures that any binary data — including images, executables, and encrypted bytes — can be safely transmitted through channels that only support text, such as email, JSON, XML, and URLs.

The most common use cases for Base64 are: embedding binary data in JSON or XML (where raw bytes would break the syntax), encoding images as data URIs in HTML/CSS, encoding JWT token payloads, transmitting credentials in HTTP Basic Auth headers, and storing binary data in text-based databases or configuration files.

Standard vs. URL-safe Base64

Standard Base64 uses + and / as two of its 64 characters. These characters have special meanings in URLs (+ means space, / is a path separator), which can cause problems when Base64 strings appear in URLs or file names. URL-safe Base64 (RFC 4648 §5) replaces + with - and / with _, and typically omits the = padding character.

JWT tokens use URL-safe Base64 for encoding the header and payload. If you try to decode a JWT payload with standard Base64, you may get an error because - and _ are not valid standard Base64 characters. Our tool handles both formats — simply toggle the URL-safe option to match your input.

Base64 is not encryption

Base64 provides no security or confidentiality. Anyone who has the Base64 string can decode it back to the original data in milliseconds. Never use Base64 to protect passwords, API keys, or other secrets. If you need to protect data, use a proper encryption algorithm like AES-256. Base64 is only useful for ensuring data compatibility across systems, not for security.

Cas d'utilisation courants

Real-world scenarios where a Base64 encoder/decoder is essential.

JWT Tokens

Decode JWT header and payload by Base64-decoding each part. Essential for debugging authentication flows.

Data URIs

Encode images, fonts, or small files as Base64 data URIs for embedding directly in HTML, CSS, or JSON.

Configuration Files

Encode binary data or special characters in YAML, JSON, or XML configuration files where raw bytes are not allowed.

API Credentials

Encode API keys and secrets for HTTP Basic Auth headers or other credential-passing mechanisms.

How does this compare to other Base64 tools?

Une comparaison côte à côte des outils populaires d'encodage Base64.

Fonctionnalité	NovaTools	Base64Encode.org	Browser btoa()
Confidentialité (sans téléversement)	100% local	Téléverse vers le serveur	Local
Mode URL sécurisé			Manual
Support UTF-8			btoa() fails on non-ASCII
Conversion en temps réel		Button click	N/A
Auto-detect mode			N/A
Compatible mobile		Limité	N/A
Fonctionne hors ligne	Après chargement

Base64Encode.org uploads your data to their server. Our tool processes everything locally — your text never leaves your browser.

Base64 Quick Reference

Key facts about Base64 encoding.

Character Set

Symbole / Code	Description	Exemple
`A-Z`	Uppercase letters (26 characters).	`QUJDRA== (encodes ABCD)`
`a-z`	Lowercase letters (26 characters).	`YWJjZA== (encodes abcd)`
`0-9`	Digits (10 characters).	`MDEyMzQ= (encodes 01234)`
`+ /`	Standard Base64 special characters. + becomes - and / becomes _ in URL-safe mode.	`Pj8+Pw== (encodes >?>?)`
`=`	Padding character (0-2 at end). Omitted in URL-safe mode.	`aGk= (encodes hi, 1 pad)`

A-Z

Uppercase letters (26 characters).

Exemple:QUJDRA== (encodes ABCD)

a-z

Lowercase letters (26 characters).

Exemple:YWJjZA== (encodes abcd)

0-9

Digits (10 characters).

Exemple:MDEyMzQ= (encodes 01234)

+ /

Standard Base64 special characters. + becomes - and / becomes _ in URL-safe mode.

Exemple:Pj8+Pw== (encodes >?>?)

=

Padding character (0-2 at end). Omitted in URL-safe mode.

Exemple:aGk= (encodes hi, 1 pad)

Key Facts

Symbole / Code	Description	Exemple
`3 → 4`	Every 3 input bytes become 4 Base64 characters.	`abc → YWJj (3 bytes → 4 chars)`
`33%`	Base64 output is approximately 33% larger than input.	`300 bytes → 400 chars`
`UTF-8`	Text is encoded as UTF-8 bytes before Base64 encoding.	`é → w6k= (2 UTF-8 bytes)`
`Not encryption`	Base64 provides no security. Anyone can decode it.	`dGVzdA== → test (instantly reversible)`

3 → 4

Every 3 input bytes become 4 Base64 characters.

Exemple:abc → YWJj (3 bytes → 4 chars)

33%

Base64 output is approximately 33% larger than input.

Exemple:300 bytes → 400 chars

UTF-8

Text is encoded as UTF-8 bytes before Base64 encoding.

Exemple:é → w6k= (2 UTF-8 bytes)

Not encryption

Base64 provides no security. Anyone can decode it.

Exemple:dGVzdA== → test (instantly reversible)

Questions fréquentes

A quoi sert Base64?

Base64 transforme du texte ou des donnees binaires en caracteres ASCII pour les utiliser dans JSON, les URLs, les e-mails, les tokens et les fichiers de configuration.

L'outil prend-il en charge Unicode?

Oui. Il utilise UTF-8 et peut traiter correctement les accents, les emoji et les textes multilingues.

Mon texte est-il envoye a un serveur?

Non. La conversion se fait localement dans votre navigateur et votre saisie ne quitte pas votre appareil.

What is Base64 encoding used for?

Base64 turns binary or text data into ASCII characters so it can safely travel through JSON, URLs, emails, tokens, and configuration files. It is commonly used to embed images in CSS/HTML (data URIs), encode JWT payloads, transmit binary data over text-only protocols, and store binary blobs in databases that only support text. Base64 is not encryption — it provides no security or confidentiality. Anyone can decode Base64 back to the original data.

Cet outil prend-il en charge le texte Unicode ?

Yes. The encoder uses UTF-8, so text with accents, emoji, Chinese, Japanese, Korean, and other scripts can be encoded and decoded correctly. The tool first converts the input string to a UTF-8 byte sequence, then encodes those bytes to Base64. On decode, it reverses the process. This avoids the common 'btoa() does not work with non-ASCII characters' error that occurs when using the native browser btoa() function directly.

Mon texte est-il téléversé vers un serveur ?

No. Encoding and decoding happen locally in your browser with JavaScript. Your input never leaves your device. You can verify this by opening your browser's DevTools Network tab — no network requests are made when you encode or decode. This makes the tool safe for encoding API keys, tokens, credentials, and other sensitive data.

What is the difference between standard and URL-safe Base64?

Standard Base64 uses the characters A-Z, a-z, 0-9, +, and /, and pads the output with = characters. The + and / characters can cause problems in URLs and file names. URL-safe Base64 replaces + with - and / with _, and typically omits the = padding. URL-safe Base64 is used in JWT tokens, data URIs, and other contexts where the encoded string appears in a URL or file name. Our tool lets you toggle between standard and URL-safe modes.

Can I encode binary files (images, PDFs)?

This tool is designed for text encoding and decoding. For binary files, use a tool that reads the file as an ArrayBuffer and converts it to Base64. However, you can use this tool to decode a Base64 string that represents a binary file (like a data URI) and inspect the MIME type. For encoding images as Base64 data URIs, our Image Converter tool handles this automatically.

Why does my Base64 string not decode correctly?

The most common cause is a character encoding mismatch. If the original text was encoded as UTF-8 but decoded as Latin-1 (ISO 8859-1), non-ASCII characters will appear garbled. Another common issue is URL-safe Base64 being decoded as standard Base64 (or vice versa) — the - and _ characters are not valid in standard Base64. Make sure you select the correct mode (standard or URL-safe) for your input. Finally, check that the input string has the correct length — Base64 strings should have a length that is a multiple of 4 (after padding).

Is Base64 encryption?

No. Base64 is an encoding scheme, not encryption. Encoding converts data from one format to another using a publicly known algorithm, and anyone can decode it. Encryption uses a secret key to scramble data so that only someone with the key can read it. Never use Base64 to protect sensitive data — use proper encryption (AES, RSA) instead. Base64 is only useful for ensuring data compatibility across systems that handle text differently.

How much larger is Base64 compared to the original data?

Base64 encoding increases data size by approximately 33%. Every 3 bytes of input becomes 4 characters of Base64 output. For example, a 300-byte input produces a 400-character Base64 string. This overhead is the trade-off for ensuring the encoded data contains only ASCII characters that are safe to transmit over text-only channels. If bandwidth is critical, consider using a binary format instead of Base64.

L'outil fonctionne-t-il sur les appareils mobiles ?

Yes. The tool is fully responsive and works on iOS Safari and Android Chrome. The interface adapts to small screens with a stacked layout — input on top, output below, and mode controls accessible via toggle buttons. The encoding and decoding process runs locally on your phone, so it works even on slow network connections.

Puis-je utiliser ceci pour des projets commerciaux ?

Oui. L'outil est gratuit pour un usage personnel et commercial, sans filigrane, sans attribution requise et sans limite d'utilisation. Vous conservez la pleine propriété de vos données. Aucune inscription, aucune clé API et aucun abonnement requis.

Votre confidentialité est notre priorité

Cet outil fonctionne entièrement dans votre navigateur. Vos fichiers ne sont pas téléversés vers un serveur, ni stockés, ni analysés.

Nous ne téléversons, ne stockons ni n'analysons vos fichiers.
Tout ce que vous traitez reste sur votre appareil.
Il n'y a pas de traitement côté serveur, ni de stockage cloud, ni d'analyse.

Même si votre connexion internet tombe, vos fichiers restent en sécurité.

Guides utiles

Comment encoder et décoder du texte Base64 en sécurité

Comprenez Base64, la différence entre Base64 standard et compatible URL, et encodez ou décodez du texte localement dans le navigateur.

Comment décoder un token JWT (Header, Payload, Signature)

Un JWT est composé de trois parties encodées en Base64URL : header, payload et signature. Apprenez à décoder un token et à lire ses claims iat, nbf et exp.

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Un guide complet sur la création de codes-barres et de codes QR personnalisés gratuitement en ligne. Apprenez à scanner n'importe quel code avec votre appareil photo ou une image, à comprendre les différents formats et à découvrir les utilisations courantes pour les projets professionnels et personnels.