Base64 to Base64URL Converter

What does the Base64 to Base64URL Converter do?

The Base64 to Base64URL Converter transforms standard RFC 4648 Base64 strings containing +, /, and = characters into URL-safe Base64URL format (RFC 7515). It replaces + with -, / with _, and strips trailing = padding characters by default (or preserves them optionally).

Core Concepts

Understanding Base64 to Base64URL conversion mechanics:

• Alphabet Character Replacement: Replaces URI-reserved characters + with - and / with _ to prevent percent-encoding expansion in HTTP URLs and web query strings.
• Padding Stripping: Removes trailing = padding characters by default, following RFC 7515 specifications for JWT headers, claims, and signatures.
• Input Validation: Detects existing Base64URL characters (- or _) in input and flags non-Base64 illegal characters.

How to use the tool?

1. Paste Standard Base64: Enter or paste your standard Base64 string into the input editor or click Sample.
2. Configure Padding: Optionally check Preserve '=' Padding if your downstream parser requires trailing = characters.
3. Live Convert & Copy: The tool converts instantly in real time. Click Copy or Download to export the URL-safe result.

Related Developer Utilities

If you work with Base64 encoding, URL formatting, and JWT tokens, explore these complementary tools:

• Base64URL to Base64 Converter: Add padding and convert URL-safe Base64 to standard Base64.
• Base64 Decoder: Decode Base64 payloads into UTF-8 text or JSON.
• Base64 Encoder: Encode plain text into Base64 or URL-safe Base64.
• URL Encoder & Decoder: Encode and decode URI query parameters.

REST API Integration

blueutils.com provides a free REST API endpoint (POST https://blueutils.com/api/base64/base64-to-base64url) to programmatically convert standard Base64 strings into URL-safe Base64URL strings.

API Request Parameters

API Request Payload Examples

cURL

curl -X POST https://blueutils.com/api/base64/base64-to-base64url \
  -H "Content-Type: application/json" \
  -d '{
    "rawText": "eyJzdWIiOiIxMjM0In0+w/1==",
    "preservePadding": false
  }'

Python

import requests

url = "https://blueutils.com/api/base64/base64-to-base64url"
payload = {
    "rawText": "eyJzdWIiOiIxMjM0In0+w/1==",
    "preservePadding": False
}
headers = {"Content-Type": "application/json"}
response = requests.post(url, json=payload, headers=headers)
print(response.json())

Java

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;

public class Main {
    public static void main(String[] args) throws Exception {
        String jsonPayload = """
            {
                "rawText": "eyJzdWIiOiIxMjM0In0+w/1==",
                "preservePadding": false
            }
            """;

        HttpClient client = HttpClient.newHttpClient();
        HttpRequest request = HttpRequest.newBuilder()
            .uri(URI.create("https://blueutils.com/api/base64/base64-to-base64url"))
            .header("Content-Type", "application/json")
            .POST(HttpRequest.BodyPublishers.ofString(jsonPayload))
            .build();

        HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());
        System.out.println(response.body());
    }
}

API Response Parameters

API Response Payload Examples

Success Response (HTTP 200 OK)

{
  "isValid": true,
  "inputLength": 28,
  "outputLength": 24,
  "paddingRemoved": 2,
  "converted": "eyJzdWIiOiIxMjM0In0-w_1"
}

Validation Failure Response (HTTP 400 Bad Request)

{
  "isValid": false,
  "error": "Invalid standard Base64: String contains Base64URL characters (\"-\" or \"_\")."
}

Rate Limit Exceeded Response (HTTP 429 Too Many Requests)

{
  "error": "API rate limit exceeded. Please wait or contact support@blueutils.com."
}

Why use an API to convert Base64 to Base64URL?

Integrating the Base64 to Base64URL API into OAuth services, JWT signing pipelines, or AI agent tool calling provides essential advantages:

• Rapid Script Validation: Safely formats encrypted tokens for transmission within URL query parameters and HTTP redirection headers without percent-encoding bloat.
• Optimized Token Efficiency for AI Agents: LLMs often retain = padding characters in URL-safe outputs. Calling the API normalizes strings deterministically without hallucination.
• Deterministic Accuracy Without Hallucinations: Ensures 100% strict character mapping and configurable padding retention.

Native Usage

How to convert standard Base64 to Base64URL locally in terminal environments or scripts:

Windows (CMD / PowerShell)

# Convert Base64 to Base64URL in PowerShell
$b64 = "eyJzdWIiOiIxMjM0In0+w/1=="
$b64url = $b64.Replace('+', '-').Replace('/', '_').TrimEnd('=')
Write-Output "Base64URL: $b64url"

Linux / Unix (Bash)

# Convert Base64 to Base64URL in Linux
echo -n "eyJzdWIiOiIxMjM0In0+w/1==" | tr '/+' '_-' | tr -d '='

Python

Using Python:

def base64_to_base64url(b64_str, preserve_padding=False):
    b64url = b64_str.replace('+', '-').replace('/', '_')
    return b64url if preserve_padding else b64url.rstrip('=')

token = "eyJzdWIiOiIxMjM0In0+w/1=="
print("Base64URL:", base64_to_base64url(token))

Java

Using Java:

public class Base64ToBase64UrlExample {
    public static String toBase64Url(String base64, boolean preservePadding) {
        String urlSafe = base64.replace('+', '-').replace('/', '_');
        return preservePadding ? urlSafe : urlSafe.replaceAll("=+$", "");
    }

    public static void main(String[] args) {
        String standard = "eyJzdWIiOiIxMjM0In0+w/1==";
        System.out.println(toBase64Url(standard, false));
    }
}