Common causes

The file was truncated or incomplete. If a file upload was interrupted, or the file was cut short when it was exported from your BIM software, it won't contain all the data the checker needs. IFC files in particular can be very large, and a partial upload will produce an invalid file.

The file isn't actually an IFC or IDS file. The checker identifies files by their content, not just their file extension. If a file has been renamed with a .ifc or .ids extension but is actually a different format (a PDF, an image, a ZIP archive, etc.), it won't load.

The IFC file uses an unsupported format. Data Octopus supports IFC files in STEP format (the standard text-based .ifc format). IFC files in ifcXML format (.ifcXML) or compressed ifcZIP format (.ifcZIP) are not currently supported.

The IDS file isn't valid XML. IDS files are XML documents. If the XML is malformed (missing closing tags, invalid characters, encoding problems) the checker can't parse it. This can happen if the file was edited by hand and an error was introduced, or if it was generated by software that produced invalid XML.

The IDS file doesn't conform to the IDS schema. The file might be valid XML but not follow the structure that the buildingSMART IDS standard requires. This is different from content errors (which are about what the rules say). This is about the file not being a valid IDS file at all.

How to check your files

For IFC files:

Try opening the file in a free IFC viewer such as BIM Vision, Xbim Xplorer, or the Trimble Connect web viewer. If the viewer can't open it either, the file is likely corrupt or incomplete.

Open the file in a text editor (Notepad will do for a quick check). A valid IFC file starts with ISO-10303-21; on the first line. If you see garbled characters or something completely different, it's not a standard IFC file.

Check the file size. If your model should be several megabytes but the file is only a few kilobytes, the export was probably incomplete.

For IDS files:

Open the file in a text editor or an XML editor. It should start with an XML declaration (<?xml version="1.0"...?>) and contain an <ids> root element.

If you have an XML editor, validate the file against the buildingSMART IDS schema. The schema is available at https://standards.buildingsmart.org/IDS/1.0/ids.xsd.

Try opening the file in a web browser. Most browsers will display XML files and highlight any syntax errors.

How to fix it

Re-export the IFC file. This is the most common fix. Go back to your BIM software and export the IFC file again. Make sure the export completes fully (large models can take a while) and that you're exporting in standard IFC format, not ifcXML or ifcZIP.

Re-upload the file. If you suspect the upload was interrupted, try uploading again. Check your internet connection is stable, especially for large files.

Check you're uploading the right file. It's surprisingly easy to accidentally upload the wrong file, especially when working with multiple versions or exports.

For IDS files, use a proper authoring tool. If you're creating or editing IDS files, use a tool designed for it rather than editing XML by hand. The buildingSMART IDS Editor and tools like BIMcollab can produce valid IDS files and catch errors before you save.