How to fix Error 4878 on Windows Server 2025 / Windows 11

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Troubleshooting Guide: SQL Server Error 4878 — Invalid Quote Character Specified for Bulk Load

Why This Error Happens

Error 4878 occurs when the quote character specified in a BULK INSERT, BCP, or OPENROWSET(BULK...) operation does not meet SQL Server’s requirement of being a single-byte or single Unicode character. This is typically caused by a misconfigured format file (.fmt or .xml) where the field_terminator or quote identifier contains multiple characters, an incorrect code page setting, or a corrupted/malformed format file generated by an incompatible version of the BCP utility. It can also happen when a multi-character string (like "" instead of ") is mistakenly passed as the quote delimiter in the import command.

Step-by-Step Resolution Guide

Step 1: Inspect the Bulk Load Command Syntax

  • Open the T-SQL script or application code calling BULK INSERT or OPENROWSET(BULK...).
  • Verify the QUOTE or delimiter argument is a single character, e.g., QUOTE = '"' and not QUOTE = '""' or a string literal with hidden whitespace.
  • Check for accidental concatenation of escape characters (e.g., \" interpreted as two bytes instead of one).

Step 2: Validate the Format File (.fmt or .xml)

  • Navigate to the format file location (commonly in the same directory as the source data file or a shared path like C:\SQLData\Import\).
  • Open the .fmt file in a plain text editor and confirm the terminator field (e.g., "\",\"") uses correctly escaped single-byte sequences.
  • If using an XML format file, check the <FIELD> element’s TERMINATOR attribute for malformed Unicode escape sequences.
  • Regenerate the format file using the BCP utility with the correct version flag:
  bcp YourDatabase.dbo.YourTable format nul -c -t, -f C:\SQLData\Import\NewFormat.fmt -S YourServerName -T

Step 3: Confirm Code Page and Collation Compatibility

  • Open SQL Server Configuration Manager and verify the server-level collation under Server Properties > Advanced.
  • Ensure the source file’s encoding (ANSI, UTF-8, or UTF-16) matches the CODEPAGE parameter used in the bulk command.
  • If importing Unicode data, explicitly set CODEPAGE = 'RAW' or CODEPAGE = '65001' for UTF-8, and ensure the quote character specified is a valid single Unicode code point (not a surrogate pair).

Step 4: Rebuild the Bulk Insert Statement with Safe Defaults

  • Rewrite the command using default, known-safe delimiters to isolate the issue:
  BULK INSERT YourTable
  FROM 'C:\SQLData\Import\datafile.csv'
  WITH (
      FIELDTERMINATOR = ',',
      ROWTERMINATOR = '\n',
      FORMAT = 'CSV',
      FIELDQUOTE = '"'
  );
  • Run the statement in SQL Server Management Studio (SSMS) connected to your SQL Server 2025 instance to confirm the error is resolved before reintroducing custom formatting.

Alternative or Verification Steps

  • Run the corrected BULK INSERT statement against a small sample dataset (5–10 rows) in a test database to confirm Error 4878 no longer appears before executing on production data.
  • If the error persists, bypass format files entirely by using the FORMAT = 'CSV' option introduced in newer SQL Server versions, which uses built-in CSV parsing logic instead of custom quote/terminator definitions.