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.DII file extension

To open .DII files on Windows, if you have Summation installed, open the software and use its load/import function to import the Summation (DII) load file (do not rely on double-click).

To open a .DII file, use litigation support/eDiscovery software that supports Summation load files (DII), such as Summation, or import it into a tool that can read Summation load formats (e.g., Nuix Workstation). If you only need to inspect it, a .DII file is usually plain text and can be viewed in a text editor, but that will not load the related images or metadata automatically.

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Last updated: June 11, 2026 · Reviewed by Julian Stricker

What “reviewed” means on this page
  • Format fit: whether the “what is this file?” description matches common real-world use of the extension, including category, typical MIME types, and aliases.
  • Opening paths: whether Windows / macOS / Linux steps read plausibly for current OS dialogs and default apps; we remove fantasy menus and unsafe shortcuts.
  • Security framing: whether risk notes match the extension class (for example executables vs plain data) and whether affiliate wording does not contradict the security section.
  • Sources and further reading: whether external links point to vendors, standards bodies, or other primary references where possible; we avoid inventing details we cannot ground.
  • Limits: this is clarity and safety-messaging QA, not a guarantee that every statement is exhaustive or that every binary you download is harmless.

Full methodology in the Imprint — The Imprint also states where AI is used and what that does—and does not—replace.

Open on your device

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

How to open .DII files

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

Windows

  1. If you have Summation installed, open the software and use its load/import function to import the Summation (DII) load file (do not rely on double-click).
  2. If you use Nuix Workstation, import the legal export/load file and select the option for Summation load files when prompted.
  3. To inspect the contents, open the .DII in a plain-text editor to review tags/records (this will not load linked images).
Full Windows guide

Mac

  1. If you have an eDiscovery tool that supports Summation load files (e.g., Nuix Workstation on macOS), use its import function and select the Summation/DII format.
  2. To inspect the file only, open it with a text editor to view the tagged records and referenced file paths.
Full Mac guide

Linux

  1. Linux typically does not have common native desktop apps for Summation DII workflows; the usual approach is to transfer the full production set to a supported desktop environment or eDiscovery platform that can import Summation load files.
  2. If you only need to read the text, open the .DII in a text editor to review records and referenced image paths.
Full Linux guide

iOS

  1. iOS generally cannot import Summation DII load files directly; for practical use, transfer the file (and its accompanying images/production set) to a desktop eDiscovery tool that supports Summation load files. If needed, open it in a text editor app just to view the raw text.
Full iOS guide

Android

  1. Android generally cannot import Summation DII load files directly; transfer the .DII and the associated production set to a desktop eDiscovery tool that supports Summation load files. You may view the raw text in a text editor app if inspection is all you need.
Full Android guide

Security notes

  • Treat .DII as untrusted input when it comes from outside your organization: it can contain file paths and references that may cause an import tool to attempt to open unexpected external files.
  • Prefer importing .DII files inside controlled eDiscovery/litigation support environments and only alongside the intended accompanying production set; avoid mixing in unrelated directories.
  • If you inspect the file in a text editor, do not run or “execute” anything—.DII is a load/metadata file, and its value is in how import tools parse it; parser vulnerabilities are a risk with any complex importer.

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.

Avast

Avast offers free and premium antivirus software that protects against viruses, malware, ransomware, and phishing. Scan files before opening them to ensure safety.

Norton

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Can't open this file?

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

Common reasons

  • Double-clicking opens in the wrong program (or not at all)
  • Import fails because referenced images/files are missing
  • Records import but fields look misaligned or incorrect

Fix steps

  1. Open your litigation support/eDiscovery application and use its load/import workflow for Summation (DII) load files.
  2. If you only need to inspect it, open it in a text editor to confirm it contains load records and not binary data.

OS-specific troubleshooting

What is a .DII file?

A .DII file is a load file format commonly associated with Summation, used to load document-level information and connect records to corresponding image files in an eDiscovery/litigation support workflow. The file contains structured records and tags that describe documents/pages and related fields, enabling a receiving system to reconstruct a production or image set during import.

Background

In legal and eDiscovery workflows, “load files” are used to transfer document metadata and relationships (like document boundaries and links to images) between systems. The DII extension is commonly used by Summation for this purpose, so you will often encounter .DII alongside image files (e.g., TIFF) and other production artifacts.

A DII file typically acts as an instruction/manifest file: it tells the target application how to ingest a batch—what each document record is, which images belong to it, and what fields should be populated. Because it is meant for automated import, double-clicking it may not “open” it in a meaningful way unless you have compatible litigation support software installed.

If you received a .DII without the referenced images or accompanying production files, it may not be usable on its own. In many cases, it is best handled as part of the complete load/production package and imported into the intended review or litigation support system.

Common MIME types: application/DII

Further reading

Authoritative resources for more details on the .DII format.

Common .DII issues

Double-clicking opens in the wrong program (or not at all)

A .DII is usually meant to be imported by litigation support/eDiscovery software, so the OS may not know what app to use.

  1. Open your litigation support/eDiscovery application and use its load/import workflow for Summation (DII) load files.
  2. If you only need to inspect it, open it in a text editor to confirm it contains load records and not binary data.

Import fails because referenced images/files are missing

DII commonly references external image/document files; if you only received the .DII, the import cannot resolve those links.

  1. Ask for the complete production package (the image files and any accompanying load/production artifacts) in the original folder structure.
  2. Verify that referenced file paths/filenames in the .DII match what is present on disk before importing.

Records import but fields look misaligned or incorrect

Load formats rely on specific tag/record structures; if the expected structure differs, fields can map incorrectly.

  1. Confirm the receiving tool is set to interpret the file as a Summation load file (DII) format during import.
  2. Open the .DII in a text editor and check whether the tagged structure matches the expected Summation DII specification used by your workflow.

FAQ

Is a .DII file just text?

In most Summation load file uses, it is a structured text file containing tagged records. You can often view it in a text editor, but the meaningful action is importing it into compatible software.

Why did I receive a .DII file with a folder of TIFF images?

That is a common pattern in legal productions: the .DII is the load file that links documents/metadata to the corresponding image files so they can be loaded into litigation support software.

Can I convert a .DII by renaming the extension?

No. Renaming does not convert the underlying format. If you need another load format, use an export/conversion feature in an eDiscovery tool that supports legal load files.

What is the correct MIME type for .DII?

IANA lists a registered media type for DII as application/DII.

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