DEVONthink supports importing many different file types. However, here are thousands of types and we can't guarantee trouble-free importing or usefulness with every type.

If DEVONthink does not recognize a file, make sure the file has a proper file name extension. DEVONthink needs a file name extension to determine the file type. Add the correct file name extension to your files, e.g., .txt for plain text files, etc.

There are only a few files that are explicitly not importable: Finder aliases or other databases, e.g., dtBase2, or items located in the internals of other databases.

DEVONthink uses Apple's Quick Look technology to display previews of many file formats. If a document is not properly displayed, especially if it is a proprietary file format, it may be you don't have a QuickLook plugin installed for this file type or the application that created the file is not installed on your Mac (and supports Quick Look). Control-click the file and choose Show In Finder to reveal it. With the file selected in the Finder, press the spacebar to open a Quick Look window to determine if the item is viewable.

Merely importing a file doesn't mean it's immediately searchable. For example, images are not content-searchable unless you've used AI transcription, set to Searchable Text or Comments.

For proprietary formats, you need to have a Spotlight importer installed. These components come from third-parties, typically the developer of the format or an application that can edit it. If there is a Spotlight importer available for the file format you're adding to your database, DEVONthink may be able to use it to gather some information about the document. The kind and amount of information is dependent on how the importer was developed.

PDFs: PDFs have been around so long, it would seem they'd be easily supported in DEVONthink. However, the truth is there are many bad PDFs out there. If you encounter a bad PDF, try acquiring a new copy of the file.

If you're having an issue annotating or editing a PDF, it's possible it is encrypted or read-only. This will be indicated with either a or property icon in the Navigation bar. You may be able to clear a read-only status with the Data > Convert > To PDF (Paginated) command.

If the file is encrypted in such a way as to inhibit changing the document, DEVONthink will honor the restrictions imposed by the document's producer. However, one potential solution for this problem is Michele Balistreri's PDFKey. It allows you to print protected PDFs. Use PDFKey to "print" a PDF file into a new PDF that is both printable and editable, which allows DEVONthink to extract the text for searching and classifying.

DEVONthink uses Apple's PDFKit framework, the same as found in their Preview application. If you have an issue with a PDF in DEVONthink, check to see if you have the same issue in Preview. Other applications, including those from Adobe where PDFs were invented, are using their own frameworks so their behavior isn't directly comparable.

Text Files: If you have an issue with plain or rich text documents, open them in TextEdit and see if the behavior is the same. DEVONthink uses macOS' text engine, so if there's an issue in our software it's likely you will see the same issue in TextEdit.