Encoding binary files as text for transfer using BASE64

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Changes to SQL introduced in SQL Server 2025 Part five of a five-part series of blogs
In addition to handling AI models, vectors of data and JSON, SQL now includes a number of other new functions and features (as this blog explains) REGEX regular expression functions Fuzzy string matching Getting the current date (and not the date/time) Using the new UNISTR function to display Unicode characters Encoding binary files as text for transfer using BASE64_ENCODE (this blog)

Changes to SQL introduced in SQL Server 2025

Part five of a five-part series of blogs

In addition to handling AI models, vectors of data and JSON, SQL now includes a number of other new functions and features (as this blog explains)

REGEX regular expression functions
Fuzzy string matching
Getting the current date (and not the date/time)
Using the new UNISTR function to display Unicode characters
Encoding binary files as text for transfer using BASE64_ENCODE (this blog)

Posted by Andy Brown on 25 November 2025

You can use the following two functions to convert between binary and text formats:

Function	What it does	Accepts	Outputs
BASE64_DECODE	Converts text to binary	varchar(n) or varchar(max)	varbinary(8000) or varbinary(max)
BASE64_ENCODE	Converts binary to text	varbinary(8000) or varbinary(max)	varchar(n) or varchar(max)

The BASE64_ENCODE function has an additional optional argument which specifies whether the output from the function should be safe to use in a website URL (this defaults to 0, or false). Here's an example of both functions in action:

-- create a variable to hold text in binary format

DECLARE @EncodedOwl as varbinary(max) = Base64_Decode('Wise Owl')

-- create a variable to hold this decoded text

DECLARE @DecodedOwl as nvarchar(max) = Base64_Encode(@EncodedOwl)

-- show these two variables

SELECT

'Wise Owl' as 'original',

@EncodedOwl as 'As binary',

@DecodedOwl as 'As text'

Here's what this SQL would give:

The result from running this function (notice that we haven't quite got back what we started with).

This function will be most useful for converting binary data like images to text format for (say) emailing; the results can then be re-encoded back to binary by the recipient.

Parts of this blog
REGEX regular expression functions Fuzzy string matching Getting the current date (and not the date/time) Using the new UNISTR function to display Unicode characters Encoding binary files as text for transfer using BASE64_ENCODE (this blog)