Tab-Separated Values MIME Type

What does text/tab-separated-values mean?

The text/tab-separated-values media type identifies tab-separated values, usually shortened to TSV. A TSV file stores a table as plain text: each line is a record, and horizontal tab characters separate fields within that record. The registered filename extension is .tsv, and there is no distinctive magic number.¹

TSV is useful when the values themselves commonly contain commas. A name such as Seattle, WA needs quoting in many CSV files but does not conflict with a tab delimiter. That simplicity comes with a firm constraint in the IANA definition: fields cannot contain literal tabs, and records are single lines.¹

How is a TSV file structured?

The IANA registration describes a header line containing field names, followed by one or more records. Every record has the same number of fields. Tabs separate the names and values, while an end-of-line sequence separates records.¹

For example, the visible spacing below represents tab characters:

name    city    postal_code
Ada London  SW1A 1AA
Lin Seattle, WA 98101

The format has no formal quoting system comparable to RFC 4180 CSV. The registration recommends escaping a tab, newline, carriage return, or backslash inside data as \t, \n, \r, or \\. That convention only works when producer and consumer agree to decode the escapes. A generic TSV reader may leave those two-character sequences untouched.¹

Where did text/tab-separated-values come from?

Paul Lindner of the University of Minnesota Internet Gopher Team registered the media type with IANA in June 1993.² The registration itself serves as the de facto specification. Unlike CSV, which later received a common format description in RFC 4180, TSV has no separate standards document that resolves every detail of encoding, escaping, headers, or line endings.³

That loose specification explains why real files differ. Some omit the header row, some use .txt, and applications may choose their own character encoding or newline convention. For reliable interchange, document the encoding, whether a header is present, and how embedded control characters were escaped.

How do you open a .tsv file?

Microsoft Excel, Apple Numbers, LibreOffice Calc, database tools, and ordinary text editors can open tab-delimited data. Excel can import a delimited text file and lets you select the tab separator, character encoding, and column interpretation.⁴ Numbers can import delimited text and lets you adjust parsing settings when columns are not detected correctly.⁵

Current Chrome, Edge, Firefox, Opera, and Safari can retrieve a text/tab-separated-values resource. Depending on response headers and local settings, the browser may show the source as text or download it. Browsers do not promise a spreadsheet grid for this media type, so use a spreadsheet or data tool when column alignment matters.⁶

Because TSV has no magic number, changing a file's extension does not convert it. A file named .tsv should still be checked for a consistent tab-delimited structure and a known character encoding.

Support in Poly

Poly recognizes text/tab-separated-values and indexes its readable content. You can search for an exact header or value, or use semantic search to find a relevant dataset by meaning. Poly also records ordinary file details such as the name and size.

Files carrying this media type use Poly's spreadsheet-oriented preview. That preview depends on a connected service and may not be available in every environment. Poly preserves the original file, so you can always download it and open it in a spreadsheet or text editor.

Poly's file-reading tools can retrieve the TSV as text, allowing the agent to inspect headers, rows, and values. TSV does not declare durable types or relationships, so the agent must infer whether a field represents a date, identifier, measurement, or other value. Provide a data dictionary when those meanings matter.

TSV compared with CSV and spreadsheets

CSV is usually the safer choice when fields may contain tabs or line breaks because its common syntax defines how to quote those characters. TSV can be easier to inspect with line-oriented tools when tabs are rare in the data. Neither format includes a schema, so both benefit from separate documentation for column names, types, units, and missing-value markers.

When exporting a workbook, remember that text formats keep only displayed text and values from the active sheet. Microsoft warns that formatting, graphics, objects, and other workbook content are lost when a worksheet is saved as tab-delimited text.⁷

Security and privacy considerations

TSV is passive text, but a spreadsheet application can interpret some cell values as formulas. If untrusted data begins with formula-triggering characters, opening the export may cause the spreadsheet to evaluate it. OWASP documents this class of issue for delimiter-separated exports. Treat TSV from untrusted sources with the same care, and validate mitigations in the exact spreadsheet applications your users rely on.⁸

TSV also has no built-in encryption, integrity protection, access control, or sensitivity labels. Review exports for personal data, hidden identifiers, and unexpected columns before sharing them. Use transport and storage protections appropriate to the dataset.