# encodeBase64ToBase64Url

## `encodeBase64ToBase64Url` Function

The `encodeBase64ToBase64Url` function transforms a standard **Base64-encoded string** into a **Base64URL-safe format**, which is commonly used in web tokens, URLs, and other contexts where Base64 characters (`+`, `/`, `=`) may be problematic.

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### Purpose

Use this function when you need to:

* Convert a **Base64-encoded value** into a **Base64URL-safe variant**
* Ensure compatibility with URL-safe systems such as JWT (JSON Web Tokens)
* Pass encoded values in query strings or API endpoints

> 🔗 Specification: [Base64URL Standard – base64.guru](https://base64.guru/standards/base64url)

***

### Function Definition

| Property          | Description                         |
| ----------------- | ----------------------------------- |
| **Function Name** | `this.encodeBase64ToBase64Url`      |
| **Type**          | `function`                          |
| **Available In**  | Server-Side Variables               |
| **Returns**       | `string` (Base64URL-encoded string) |

***

### Parameters

| Parameter | Description                   | Type     | Required                                      | Example      |
| --------- | ----------------------------- | -------- | --------------------------------------------- | ------------ |
| `input`   | A valid Base64-encoded string | `string` | <i class="fa-square-check">:square-check:</i> | `"YWJjKys="` |

***

### Conversion Behavior

This function applies the following transformations:

| Base64 Character | Replaced With (Base64URL) |
| ---------------- | ------------------------- |
| `+`              | `-`                       |
| `/`              | `_`                       |
| `=`              | *(removed)*               |

***

### Example Usage

```js
async function() {
    let x = this.encodeBase64ToBase64Url("YWJjKys="); // Base64 of "abc++"
    return x; // → "YWJjKys"
}
```

This converts the Base64 string `"YWJjKys="` into a **Base64URL-safe** format by removing `=` padding and replacing special characters.

***

### Use Cases

* Encode payloads or claims for **JWT (JSON Web Token)**
* Safely pass encoded values in **URLs or query parameters**
* Normalize Base64 data for systems that **reject or mishandle special characters**

***

### Notes

* The input must be a valid **Base64-encoded** string. This function does not encode raw values — it **only converts** Base64 → Base64URL.
* For Base64 encoding of raw input, use native methods or pre-process before using this function.
* The resulting output will contain only **URL-safe characters**.

***

### Summary

`this.encodeBase64ToBase64Url` allows you to convert standard Base64 strings into the Base64URL format required by web standards like JWT. This ensures compatibility in environments where Base64 special characters can cause issues.