.DL file extension

To open .DL files on Windows, right-click the .dl file → Open with → choose a text editor to inspect it as plain text.

To open a .dl file, use a text editor to view it as plain text, or open/run it with a Datalog system (for example, Soufflé uses <program>.dl files). If you are unsure what created the file, open it in a text editor first rather than renaming the extension.

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Last updated: April 30, 2026 · Reviewed by Julian Stricker

Open on your device

Choose your operating system for a dedicated step-by-step opening guide.

How to open .DL files

Use these platform-specific instructions to open .DL files safely.

Windows

Right-click the .dl file → Open with → choose a text editor to inspect it as plain text.
If the content looks like Datalog rules/facts, open it with a Datalog tool that supports .dl programs (for example, Soufflé).
If Windows asks what app to use, do not rename the file; instead, identify the producing tool/workflow and install the matching Datalog tool.

Full Windows guide

Mac

Control-click the .dl file → Open With → choose a text editor to view the file contents.
If it is Datalog code, use a Datalog tool that supports .dl inputs (for example, Soufflé on macOS if installed).
If you need to share it, treat it as source code text and keep the .dl extension.

Full Mac guide

Linux

Open the .dl file in a text editor to inspect it (it should be readable text if it is Datalog).
Run or compile it with a Datalog engine that uses .dl program files (Soufflé documentation uses <program>.dl).
If it fails to parse, confirm the file matches the Datalog Text Representation expected by your tool.

Full Linux guide

iOS

Use the Files app to open the .dl file in a text-capable viewer/editor; there is no broadly standard iOS Datalog runtime, so for execution you will typically transfer it to a desktop Datalog tool.

Full iOS guide

Android

Open the .dl file with a text editor app to read it; for running/compiling Datalog you will typically move the file to a desktop environment with a Datalog tool (such as Soufflé).

Full Android guide

Security notes

.dl (Datalog) files are typically plain text rules/facts, not executables, but untrusted files can still be risky if fed into a complex parser/compiler (crashes or resource exhaustion are possible).
If you run a .dl program in a Datalog engine, treat it like code: it can trigger heavy computation (very long runtimes or high memory usage) depending on the rules and input data.
Prefer opening unknown .dl files in a text editor first to verify they look like Datalog and to understand what they are intended to do before running them in a Datalog tool.

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Can't open this file?

These are the most common causes and fixes when .DL files fail to open.

Common reasons

The file opens as gibberish or unreadable characters
A Datalog tool refuses to parse the .dl file
The operating system does not know what app to use

Fix steps

Open it in a plain text editor and check whether it contains readable rules/facts; if not, verify where the file came from.
Re-download or re-transfer the file using a method that preserves text encoding (avoid copy/paste through apps that may alter characters).

OS-specific troubleshooting

What is a .DL file?

A .dl file is commonly a Datalog program stored in a standard textual representation, with an IANA-registered media type: application/vnd.datalog. In practice, these files contain facts and rules for Datalog engines and related tooling. Because it is text-based, a .dl file can be inspected safely with a plain text editor before using it with a Datalog compiler/interpreter.

Background

Datalog is a declarative logic programming language widely used in program analysis, static analysis, and database-style rule evaluation. Files using the .dl extension are commonly used to store Datalog programs (rules and facts) that can be loaded by Datalog tools.

The Datalog Specifications site defines a standard “Datalog Text Representation” and includes IANA considerations that match the IANA media type registration for application/vnd.datalog. This helps tool authors and users exchange Datalog programs in a consistent text format.

In real workflows, .dl files are often authored in a code editor and then executed or compiled by a Datalog engine. Soufflé’s documentation, for example, shows usage patterns based on a <program>.dl file.

Common MIME types: application/vnd.datalog

Common .DL issues

The file opens as gibberish or unreadable characters

Most .dl files for Datalog should be plain text. If it looks like binary data, it may not be a Datalog file (or it may be corrupted/incorrectly transferred).

Open it in a plain text editor and check whether it contains readable rules/facts; if not, verify where the file came from.
Re-download or re-transfer the file using a method that preserves text encoding (avoid copy/paste through apps that may alter characters).

A Datalog tool refuses to parse the .dl file

Different tools may accept different syntaxes; even within Datalog, dialect differences can cause parse errors.

Confirm the tool’s expected syntax and compare it with the Datalog Text Representation specification.
Look for common issues such as unsupported predicates, syntax differences, or encoding problems (for example, unusual quotes or non-UTF-8 text).

The operating system does not know what app to use

.dl is associated with Datalog text (application/vnd.datalog), but most systems do not ship with a dedicated Datalog IDE by default.

Open the file in a text editor to confirm it is Datalog source.
Install and use a Datalog system that supports .dl programs (for example, Soufflé) or keep using a text editor for viewing/editing.

FAQ

Is a .dl file just text?

In the common Datalog meaning, yes: it is a text representation of a Datalog program (rules and facts) and can be viewed in any text editor.

What is the official MIME type for Datalog .dl files?

IANA registers application/vnd.datalog and lists the file extension as .dl.

Can I convert a file to .dl by renaming it?

No. Renaming only changes the extension. To produce a valid .dl Datalog text file, you must export or write it in a Datalog text syntax accepted by your target tool/specification.

What software can work with .dl Datalog programs?

Datalog engines and tools can use .dl programs; Soufflé documentation explicitly demonstrates using a <program>.dl file.

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