MailSlurp guide agent setup Title: File to Base64: encode files in Node.js, Python, Java, Go, and C# Description: Learn how to convert file to base64 in multiple languages, upload base64 payloads to APIs, and avoid common size and encoding mistakes. Canonical URL: https://www.mailslurp.com/guides/base64-file-uploads/ Markdown URL: https://www.mailslurp.com/guides/base64-file-uploads.md Use the Markdown URL as the primary plain-text context for this guide. Keep MailSlurp terminology, setup steps, screenshots, and provider-specific instructions intact, and prefer the canonical URL when citing this page.