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How to open .CWL files on iOS

To open .CWL files on iOS, iOS typically does not run CWL workflows natively; open the .cwl file in a text/code viewer to read it, or transfer it to a desktop/Linux environment to execute it with a CWL runner.

Step-by-step instructions

  1. iOS typically does not run CWL workflows natively; open the .cwl file in a text/code viewer to read it, or transfer it to a desktop/Linux environment to execute it with a CWL runner.

Alternative methods

  • Open .CWL in a browser-based viewer if desktop apps fail.
  • Try opening .CWL on iOS with a secondary app to rule out app-specific issues.
  • Convert .CWL only with trusted tools when direct opening is not possible.

Common issues

The .CWL file opens as text but does not “run”

A .cwl file is a workflow/tool description, not a standalone program. It must be executed by a CWL runner, usually together with an inputs object file and the required tools/containers.

  1. Run the file using a CWL executor (for example, the cwltool reference implementation) rather than double-clicking it.
  2. Check whether the workflow expects a separate input parameters file (often YAML/JSON) and provide it when running.
  3. Ensure the referenced command line tools or containers are available in your environment.

Runner reports validation errors or “unsupported CWL version”

CWL documents declare a CWL version and must follow the specification; a runner may reject documents that don’t match the expected schema or version.

  1. Confirm the document’s CWL version and compare it with your runner’s supported versions.
  2. Validate the document structure against the CWL specification and correct missing/incorrect fields.
  3. Try another CWL implementation from the official list if your current executor lacks support for the document’s features.

Workflow starts but fails due to missing tools, paths, or containers

CWL workflows often call external command-line tools or containers; failures occur if dependencies are not present, not accessible, or differ from what the workflow expects.

  1. Review the workflow/tool requirements and ensure required software is installed or available via container references.
  2. Check file paths and input filenames in your input object; ensure referenced files exist and are readable.
  3. Run with increased logging in your executor to identify which step failed and why, then adjust environment or inputs accordingly.

File association confusion (opens in the wrong app)

Operating systems may not recognize .cwl as an executable workflow description and will open it with a default editor or unrelated program.

  1. Open it explicitly with a text editor for viewing or with your CWL runner from the command line for execution.
  2. Avoid changing the extension; instead, install/configure a CWL runner and use it to process the file.
  3. If you need consistent behavior, document a standard runner and command for your team (for example, using cwltool).

Security note

Treat .cwl files as executable instructions: running a CWL workflow can execute command line tools and may read/write files, so only run workflows from sources you trust.

Back to .CWL extension page