Base64 Encode and Decode in Excel, Google Sheets, and Notepad++

Developers and analysts who work heavily in Excel, Google Sheets, or Notepad++ sometimes need to Base64 encode or decode values without switching to a separate tool. While these applications are not primarily designed for encoding operations, there are ways to do it in each — formulas, scripts, and plugins.

This guide covers each option and explains when the simplest approach (a free browser tool) saves more time than building a formula or installing a plugin.

Base64 in Excel — VBA Macro Approach

Excel does not have built-in Base64 functions, but you can add them using VBA (Visual Basic for Applications). Here is a complete VBA function you can add to any workbook:

Function Base64Encode(sText As String) As String
    Dim oXML As Object
    Dim oNode As Object
    Set oXML = CreateObject("MSXML2.DOMDocument")
    Set oNode = oXML.createElement("b64")
    oNode.DataType = "bin.base64"
    oNode.nodeTypedValue = _
        CreateObject("ADODB.Stream").Write(sText)
    Base64Encode = Replace(oNode.Text, vbLf, "")
    Set oNode = Nothing
    Set oXML = Nothing
End Function

A simpler approach that works in most Excel versions without MSXML dependencies:

Function B64Encode(s As String) As String
    Dim b() As Byte
    b = StrConv(s, vbFromUnicode)
    With CreateObject("MSXML2.DOMDocument.6.0") _
        .createElement("b")
        .DataType = "bin.base64"
        .nodeTypedValue = b
        B64Encode = .Text
    End With
End Function

Function B64Decode(s As String) As String
    With CreateObject("MSXML2.DOMDocument.6.0") _
        .createElement("b")
        .DataType = "bin.base64"
        .Text = s
        B64Decode = StrConv(.nodeTypedValue, vbUnicode)
    End With
End Function

To add this to Excel: press Alt+F11 to open the VBA editor, insert a new Module, paste the code, and save. You can then use =B64Encode(A1) and =B64Decode(A1) as regular worksheet functions.

Base64 in Google Sheets — Apps Script

Google Sheets uses JavaScript for its Apps Script environment, which has built-in Base64 utilities via the Utilities service:

// In Apps Script (Extensions > Apps Script)
function base64Encode(text) {
  return Utilities.base64Encode(text);
}

function base64Decode(encoded) {
  return Utilities.newBlob(
    Utilities.base64Decode(encoded)
  ).getDataAsString();
}

To use these as spreadsheet functions:

1. Go to Extensions > Apps Script in your Google Sheet
2. Paste the functions above
3. Save and return to the spreadsheet
4. Use =base64Encode(A1) directly in cells

Google Sheets also has BASE64 and DEBASE64 as built-in functions in some Google Workspace editions. Check if =BASE64(A1) works in your Sheet — if it does, no script setup is needed.

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Base64 in Notepad++ — MIME Tools Plugin

Notepad++ supports Base64 encoding and decoding through the MIME Tools plugin, which comes pre-installed in most recent Notepad++ distributions:

Check if MIME Tools is installed: Go to Plugins menu and look for "MIME Tools." If it is there, you have it.

To install if missing: Plugins > Plugins Admin > search for "MIME Tools" > Install.

Encoding in Notepad++:

1. Select the text you want to encode
2. Plugins > MIME Tools > Base64 Encode
3. The selected text is replaced with its Base64 encoding

Decoding in Notepad++:

1. Select the Base64 string
2. Plugins > MIME Tools > Base64 Decode
3. The selected text is replaced with the decoded content

The MIME Tools plugin also supports URL encoding, quoted-printable, and other encoding formats from the same menu.

When the Browser Tool Saves More Time

Setting up VBA in Excel, Apps Script in Google Sheets, or finding and installing a Notepad++ plugin all take time. For one-off encoding or decoding tasks, the free browser tool is often the fastest option:

• No setup: Open a browser tab, paste the string, click Encode or Decode. Done in 10 seconds.
• No macro security warnings: Excel often blocks VBA macros and requires enabling them per-workbook. A browser tool has no such friction.
• Works when you do not have admin rights: Installing Notepad++ plugins or enabling VBA macros may require admin access in managed environments. A browser tool requires no permissions.
• Cross-platform: The browser tool works on Mac and Linux, where Excel VBA behaves differently and MIME Tools is not available.

Use the Excel/Sheets formula approach when you need Base64 as part of a larger spreadsheet workflow — processing a column of values, or building automation that encodes values dynamically. Use the browser tool when you just need to encode or decode a specific string quickly.

Decoding a Column of Base64 Values in Excel

A common analyst workflow: you receive data where one column contains Base64-encoded values (API responses, encoded identifiers, encoded configuration values) and you need to decode all of them to inspect the data.

With the VBA function from Step 1 installed:

1. Assume Base64 values are in column A, starting in A2
2. In cell B2, enter =B64Decode(A2)
3. Copy B2 down for all rows
4. Column B now shows the decoded values for every row

For a smaller dataset (under 20 values), copying them into the free browser tool one by one is faster than setting up the VBA. For a large column of hundreds of encoded values, the Excel formula approach pays off.

Note: VBA-based Base64 decoding may have issues with non-ASCII characters depending on the encoding used and the Excel locale settings. If decoded text shows garbled characters, the source data may use a different character encoding than your system expects — try testing with a known simple ASCII string first to confirm the functions work in your environment.

Frequently Asked Questions

Does Excel have a built-in BASE64 function?

Not in standard Excel as of 2026. The B64Encode and B64Decode functions require VBA code added to your workbook. Google Sheets has a built-in BASE64() function in some Workspace editions. Check if it works in your Sheet before writing a script.

Why does Notepad++ show garbled characters after decoding?

The decoded content may be binary data (not text), or the text may use a different character encoding than Notepad++ expects. MIME Tools decodes to the byte sequence — if the result was originally UTF-8 text, change the encoding in Notepad++ (Encoding menu > Encode in UTF-8) and the display should correct.

Can I Base64 encode an entire Excel file?

Yes, technically — you can read the binary file bytes and encode them. But this is not something you do inside Excel itself. You would use a programming language (Python, PowerShell) or a file-to-Base64 tool to convert the whole file. Our browser encoder handles text strings, not file uploads.