Verified Developer Solution • 100% OfflineFix "Invalid character in base64 string"
Troubleshoot Base64 parsing errors caused by whitespace, line breaks, or URL encoding.
The Problem (Error Root Cause)Exception
Your backend framework throws an "Invalid character in base64 string" error. This usually happens when copying Base64 certificates or tokens that contain newlines `\n` or when the string was URL-encoded (e.g., `%3D` instead of `=`).
Identified via runtime validation & stack traces
The Solution (Step-by-Step Fix)Verified
Strip all whitespace and newlines from the string before decoding, and ensure it has been URL-decoded if it came from a query parameter.
Deterministic, non-destructive resolution
Code Standard: Bad Pattern vs Verified Fix
Live SyntaxAnti-Pattern vs Verified Fix
1// ❌ Bad: Contains newlines2const raw = "base64\nstring\n";3 4// ✅ Good: Clean string5const clean = raw.replace(/\s+/g, '');6const decoded = Buffer.from(clean, 'base64');Test and resolve this using Base64 / Hex / Binary Multi-Inspector & Image Previewer
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Frequently Asked Questions
Q:Should Base64 have line breaks?
PEM certificates require 64-character line breaks, but standard Base64 parsing usually expects a continuous string.
Q:Can I decode it manually?
Paste it into our Base64 Inspector and we will clean and decode it for you.