What is the TAG file format?
The .tag file is a binary format associated with DataFlex technology. It stores query tag-name index information that the DataFlex database engine uses to locate records in paired DAT tables. .tag files (as well as .fd files) are named the same as their related .dat tables. Because .tag files are engine-managed internal artifacts, they should not be edited manually.
DataFlex is a technology for developing various applications using one framework-based platform. The tool allows developers to create multiplatform applications through its integrated environment. Database integration is handled using built-in tools, some of which rely on .tag files as part of the underlying flat-file database engine. Using DataFlex, developers can build desktop, web, or mobile applications for Windows and server-based systems. In modern DataFlex versions, the legacy .dat/.tag flat-file table structure has been largely superseded by SQL and embedded-database back ends; older deployments may still encounter .tag files alongside their matching .dat, .k1, .k2, and .vld table companions.
Security & safety
RISK: LOWA DataFlex .tag is passive database-engine data and not executable, so it poses little direct risk. The real risk is operational: deleting or editing a .tag inside a live DataFlex application can break that application's indexing - leave engine files to the application. If your .tag is a game asset or media sidecar it is likewise low risk; only be cautious with .tag files of unknown origin downloaded from the internet.
Format details
in a nutshell- DivX Tag / generic media tag - Small sidecar holding metadata (title, author, comments) for a video, written by some media tools.
- Generic plain-text TAG note - Some apps save a simple text file of keywords/labels with the .tag extension.
- Game/engine tag resource - Various games and engines (e.g. Halo's HEK) use .tag for compiled asset/tag resources.
Programs that open TAG files
Windows2 apps
DataFlex (Data Access Worldwide)
Paid Open the file only inside the DataFlex application/runtime that owns the matching table set; it is not a standalone document.
Text editor (only if it's actually a plain-text .tag)
Open-source If the .tag is a simple keyword/label text file (not DataFlex/binary), open it in Notepad++ to read/edit. 
Linux1 app
DataFlex runtime (server deployments)
Paid Used in place by a deployed DataFlex application; not opened manually. Technical details
deep spec| File category | Binary auxiliary database index file |
| Byte order | Little-endian |
| Typical file size | A few kilobytes; a small index sidecar, not the bulk data table |
| Paired data file | Always accompanies a .dat file of the same base name in the same DataFlex table set |
| Role in engine | Stores query tag-name index metadata the DataFlex runtime uses to locate records in the paired .dat table |
| Table set companions | .dat, .k1, .k2, .vld, .fd - all share the same base filename |
| File signature | No documented public magic bytes; engine identifies file by name and companion context, not a stable header |
| MIME type | application/octet-stream (generic binary; no registered specific MIME type) |
| Standalone usability | None - meaningless without its matching DataFlex table set; cannot be opened independently |
| Manual editing | Not safe; file is engine-managed and direct edits will corrupt the database index |
| Platform support | Windows (primary), Unix/Linux (server deployments), MS-DOS (legacy DataFlex) |
| Developer | Data Access Worldwide (engine originally by The Database Managers, Inc.) |
| Legacy status | Largely historical; modern DataFlex uses SQL and embedded-database back ends instead of .dat/.tag flat files |
| Released | 1980s, with the DataFlex 4GL database environment |
| Latest version | Tied to the embedded DataFlex DAT/index file set; superseded by SQL/embedded-DB indexing in modern DataFlex |
| Specification | www.dataaccess.com |
TAG conversions
Community Q&A
asked by usersNo questions yet - be the first to ask about TAG files.
