.TOML file extension
To open .TOML files on Windows, right-click the .toml file and choose Open with.
To open a .toml file, use a plain text editor (such as Notepad on Windows, TextEdit in plain-text mode on macOS, or a code editor). .toml files are configuration files, so they’re usually meant to be edited as text rather than “run.”
Last updated: June 12, 2026
Open on your device
Choose your operating system for a dedicated step-by-step opening guide.
How to open .TOML files
Use these platform-specific instructions to open .TOML files safely.
Windows
- Right-click the .toml file and choose Open with.
- Select a text editor (for example, Notepad) or your preferred code editor to view and edit it.
Mac
- Right-click (or Control-click) the .toml file and choose Open With.
- Open it in a text editor; if using TextEdit, set it to plain text mode to avoid rich-text formatting.
Linux
- Open the file with a text editor from your desktop environment (for example, by right-clicking and choosing Open With).
- If file associations are missing or incorrect, your system’s shared-mime-info database may not be mapping .toml as expected; you can still open it in any text editor.
iOS
- Use the Files app to locate the .toml file and open it in a text editor app that can edit plain text; if none is available, transfer it to a desktop for editing.
Android
- Open the .toml file with a text editor app that supports plain text; if editing is awkward, transfer it to a desktop and edit it there.
Security notes
- TOML files are not executable by themselves, but they can influence how developer tools behave (for example, build, packaging, or dependency settings). Review untrusted TOML before using it in your toolchain.
- Be cautious when using third-party TOML parsers in applications: malformed or adversarially crafted input can trigger parser bugs or excessive resource usage (denial-of-service) in some implementations.
- If a .toml file is part of a software project (such as Cargo.toml or pyproject.toml), treat it as code-adjacent configuration: changes can alter build outputs and dependency resolution.
If you did not expect this file
This extension is usually plain data, text, or structured content—not a program by itself. The practical risk is social engineering (a scam attachment or misleading filename). For trusted senders you rarely need heavy-handed antivirus wording; use these tools when you want an extra check on unexpected downloads.
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Can't open this file?
These are the most common causes and fixes when .TOML files fail to open.
Common reasons
- Tool reports a TOML parse error
- Double-clicking doesn’t open in the expected app
- Encoding or line-ending problems after moving between systems
Fix steps
- Validate the structure against the official TOML v1.0.0 specification (pay attention to quoting, commas in arrays, and table headers).
- If the file is Cargo.toml or pyproject.toml, compare your keys/sections to the relevant tool documentation to ensure the expected fields and layout.
OS-specific troubleshooting
What is a .TOML file?
TOML is a minimal, human-friendly configuration format designed to map cleanly to key/value data structures. The syntax uses keys and values (strings, numbers, booleans, dates/times), tables (sections), and arrays. The official TOML v1.0.0 specification states the appropriate media type is application/toml.
Background
TOML is widely used for tool configuration because it is readable and structured, while still being easy to edit by hand. In practice, you’ll often encounter it as a project configuration file in software development workflows.
Two very common real-world examples are Rust’s Cargo.toml (the manifest file for Cargo projects) and Python’s pyproject.toml (used by Python packaging tooling to declare project metadata and configuration). These files are typically consumed by the relevant tools rather than by end-user applications.
If you are using a Linux desktop environment, file type recognition may rely on the freedesktop.org shared-mime-info database, which maps filename extensions to MIME types and desktop handling rules via extension “globs” and XML definitions.
Common MIME types: application/toml
Further reading
Authoritative resources for more details on the .TOML format.
Common .TOML issues
Tool reports a TOML parse error
Configuration tools that read TOML (such as Rust Cargo or Python packaging tools reading pyproject.toml) will reject invalid TOML syntax, often stopping builds or packaging steps.
- Validate the structure against the official TOML v1.0.0 specification (pay attention to quoting, commas in arrays, and table headers).
- If the file is Cargo.toml or pyproject.toml, compare your keys/sections to the relevant tool documentation to ensure the expected fields and layout.
Double-clicking doesn’t open in the expected app
Some systems may not have a dedicated association for .toml, or the association may point to an unsuitable application.
- Use “Open with” and choose a plain text editor or code editor.
- On Linux desktops, MIME/association behavior can be influenced by the shared-mime-info database; updating or correcting associations may help, but you can always open TOML as plain text.
Encoding or line-ending problems after moving between systems
A TOML file is text; if it is saved with an unexpected encoding or altered line endings, some tooling may fail to read it correctly.
- Re-save the file as UTF-8 in a plain text editor.
- Avoid editors that silently convert the file into rich text or change formatting in non-obvious ways.
FAQ
Is a .toml file just text?
Yes. TOML is a plain-text configuration format designed to be easy for humans to read and write, and for programs to parse.
What MIME type should TOML use?
The official TOML v1.0.0 specification states the appropriate media type is application/toml.
Why do I often see Cargo.toml or pyproject.toml?
Rust’s Cargo uses Cargo.toml as the project manifest, and Python packaging tooling uses pyproject.toml to declare project metadata and configuration.
Is application/toml registered with IANA?
Check the IANA Media Types registry to confirm whether a TOML media type is officially registered there; the TOML specification itself recommends application/toml.
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