> For the complete documentation index, see [llms.txt](https://docs.blockchain.com/pay/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.blockchain.com/pay/getting-started/customise-the-widget/optional-customisation.md).

# Optional Customisation

Create seamless experiences specific to your app

{% hint style="info" %}
All query parameters used in your integration must be [URL-encoded](https://www.w3schools.com/tags/ref_urlencode.ASP) to ensure they work correctly. For example use `satoshi%40blockchain.com` for email addresses. 
{% endhint %}

## Optional Query Parameters

<table><thead><tr><th width="277">Parameter</th><th>Description</th></tr></thead><tbody><tr><td><code>baseCurrency</code></td><td>The cryptocurrency your customer will buy. <br><br>Setting this parameter means the user will not be able to specify a different currency to purchase.<br><br>Specify as the ticker symbol, for example <code>BTC</code>, <code>ETH</code>, <code>USDT</code>, etc.<br><br>(Coming soon) Support for layer-2 networks. </td></tr><tr><td><code>walletAddress</code></td><td>The default wallet address of where the customer will receive their purchased tokens. <br><br>If specified, the customer won't need to fill in their wallet address. <br><br>You must specify <code>baseCurrency</code> and <code>walletAddressSignature</code> when specifying <code>walletAddress</code>.</td></tr><tr><td><code>walletAddressSignature</code></td><td>Ensures that <code>walletAddress</code> value was not altered en-route to us.<br><br>Must be used when using the <code>walletAddress</code> parameter. See <a data-mention href="/pay/getting-started/query-parameter-signing.md">Query parameter signing</a> for how to generate the signature. </td></tr><tr><td><p><code>walletAddressTag</code> </p><p><code>(Coming soon)</code></p></td><td>The secondary cryptocurrency wallet address identifier/memo for coins such as XLM and XRP. This parameter will be skipped if <code>walletAddress</code>, <code>walletAddressSignature</code> or <code>baseCurrency</code> are not passed.</td></tr><tr><td><code>quoteCurrency</code></td><td>The currency your customer will use to buy their desired cryptocurrency. <br><br>We currently support US Dollars, Pound Sterling and Euros, specified as <code>USD</code>, <code>GBP</code>, or <code>EUR</code>.<br><br>(Coming soon) Support for more fiat currencies. </td></tr><tr><td><code>quoteCurrencyAmount</code></td><td>The default amount of fiat used to buy cryptocurrency. Users will be able to change this value.<br><br>We recommend using this parameter together with <code>quoteCurrency</code>.</td></tr><tr><td><code>email</code> </td><td>The email address of the user. <br><br>When used, the user won't need to specify their email address with us, they will skip the email entry screen and will be prompted directly for their one-time passcode.<br><br>Make sure to URL-encode the email you pass. For example use <code>satoshi%40blockchain.com</code> instead of <code>satoshi@blockchain.com</code>.</td></tr><tr><td><code>externalReference</code></td><td>A reference you assign to this order. We will include this identifier when sending you order related information. <br><br>Useful to relate order records from us to those in your internal systems. <br><br>It is limited to 100 characters.</td></tr><tr><td><code>subPartnerId</code></td><td>A reference of a 3rd party that is involved in the processing flow. We will use this information for internal metrics. <br><br>It is limited to 50 characters.</td></tr><tr><td><code>paymentMethod</code></td><td><p>The default payment method for the order. <br><br>We currently support:</p><ul><li>credit and debit card payments, specified as <code>CARD</code></li><li>Apple Pay and Google Pay payments, specified as <code>APPLE_PAY</code> and <code>GOOGLE_PAY</code> correspondingly<br></li></ul><p>(Coming soon) Many more payment methods including ACH bank transfer, GBP and EUR bank transfers, GBP and EUR Open Banking.</p></td></tr><tr><td><code>redirectUrl</code></td><td><p>A URL to which customer will be able to proceed after completing the buy flow.</p><p></p><p>The URL can include your own custom parameters.<br><br>You must specify <code>redirectUrlSignature</code> when specifying <code>walletAddress</code>.</p></td></tr><tr><td><code>redirectUrlSignature</code></td><td>Ensures that <code>redirectUrl</code> value was not altered en-route to us.<br><br>Must be used when using the <code>redirectUrl</code> parameter. See <a data-mention href="/pay/getting-started/query-parameter-signing.md">Query parameter signing</a> for how to generate the signature. </td></tr></tbody></table>