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.CDX file extension

To open .CDX files on Windows, install or use a CDX-capable chemistry tool (commonly ChemDraw; alternatively, use a toolchain that can import CDX such as Open Babel, or Wolfram Language Import).

To open a .CDX file, use a chemistry application that supports the ChemDraw Exchange format (CDX), such as ChemDraw itself or tools that can import CDX (e.g., Open Babel, Wolfram Language). If your device can’t open it directly, transfer the file to a desktop app and convert it to a more widely supported chemical format.

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Last updated: April 29, 2026 · Reviewed by Julian Stricker

Open on your device

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

How to open .CDX files

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

Windows

  1. Install or use a CDX-capable chemistry tool (commonly ChemDraw; alternatively, use a toolchain that can import CDX such as Open Babel, or Wolfram Language Import).
  2. Right-click the .cdx file → Open with → choose the installed CDX-capable app.
  3. If it still won’t open, try converting it to CDXML or another chemical format using a CDX-capable converter (e.g., Open Babel).
Full Windows guide

Mac

  1. Open the .cdx file in a CDX-capable chemistry tool (commonly ChemDraw; alternatively, use Wolfram Language Import, or convert via Open Babel).
  2. Control-click the file → Open With → select the app (use “Other…” if it’s not listed).
  3. If you need compatibility with other tools, convert the file to CDXML (the XML equivalent described in the CDX/CDXML specification) or another chemical format.
Full Mac guide

Linux

  1. Linux often won’t have a native desktop editor for CDX preinstalled; plan to convert it using a chemistry toolchain that supports CDX import (e.g., Open Babel).
  2. Use your package/command-line workflow to convert the .cdx to a more common format for your tools (for example, into another chemical structure format supported in your environment).
  3. If conversion results look incomplete, try opening the original on a system with ChemDraw and exporting again (see common issues about feature limitations).
Full Linux guide

iOS

  1. iOS typically won’t preview or edit CDX natively; transfer the file to a desktop chemistry app that supports CDX, or convert it on a desktop and then view the converted output on iOS.
Full iOS guide

Android

  1. Android typically won’t open CDX natively; transfer the file to a desktop chemistry app that supports CDX, or convert it to another chemical format on a desktop and then open the converted file on Android.
Full Android guide

Security notes

  • CDX is a complex binary format; opening untrusted CDX files in any parser/editor can carry risk of bugs in the application’s file parsing. Prefer opening files from trusted sources, especially in high-value environments.
  • If you need to inspect an unknown CDX, consider converting it with a well-maintained toolchain (or opening in a restricted environment) rather than directly opening it in your primary workstation’s chemistry editor.
  • Be cautious when receiving CDX files as email attachments: confirm the sender and context, and treat unexpected CDX files as potentially suspicious even though CDX is not an executable format.

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Can't open this file?

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

Common reasons

  • The .CDX file won’t open or shows as an unknown format
  • Converted/imported structure looks wrong or incomplete
  • File seems corrupted or partially downloaded

Fix steps

  1. Open it with a CDX-capable tool (ChemDraw is the common choice; Open Babel and Wolfram Language also document CDX support).
  2. If you’re on mobile, transfer the file to a desktop system and open/convert it there.
  3. Avoid renaming the extension; convert/export using a tool that understands CDX.

OS-specific troubleshooting

What is a .CDX file?

CDX (ChemDraw Exchange) is ChemDraw’s native tagged binary format for chemical drawings and related data. The IUPAC-hosted specification describes CDX as a structured, tagged binary format with an equivalent XML representation called CDXML. It is used as a standard chemical structure exchange format in several workflows, including use cases referenced by the specification (e.g., USPTO adoption noted in the general documentation).

Background

ChemDraw Exchange (CDX) is widely used to store 2D chemical structures, reaction schemes, and associated drawing objects created in ChemDraw-style editors. Unlike plain-text chemical formats, CDX is a compact binary format organized as tagged records, which can store rich drawing and layout information.

The format is documented in an IUPAC-hosted CDX/CDXML specification that explains how CDX maps to an equivalent CDXML representation. This CDX↔CDXML relationship is useful in practice because CDXML can be easier for some tools to process or version-control, while CDX is common for day-to-day authoring and exchange in ChemDraw-centric workflows.

For interoperability, some chemistry toolchains can import CDX. For example, Open Babel documents read support for ChemDraw binary (.cdx), and Wolfram Language documents CDX as an importable/exportable format (with the internet media type chemical/x-cdx). Preservation-oriented references (Library of Congress) also describe the format and its media type, which can help when identifying files in archives or institutional collections.

Common MIME types: chemical/x-cdx

Further reading

Authoritative resources for more details on the .CDX format.

Common .CDX issues

The .CDX file won’t open or shows as an unknown format

CDX is a specialized ChemDraw Exchange binary format and many general-purpose viewers can’t open it. This is usually due to missing chemistry software or incorrect file association.

  1. Open it with a CDX-capable tool (ChemDraw is the common choice; Open Babel and Wolfram Language also document CDX support).
  2. If you’re on mobile, transfer the file to a desktop system and open/convert it there.
  3. Avoid renaming the extension; convert/export using a tool that understands CDX.

Converted/imported structure looks wrong or incomplete

Some tools (including converters) may not preserve every drawing feature or object in a rich CDX document when importing or exporting to other formats.

  1. Try converting to CDXML first (the specification describes CDX↔CDXML equivalence), then convert from CDXML to your target format if needed.
  2. If possible, open the file in ChemDraw and export to the exact target format you need.
  3. Compare results in more than one tool (e.g., check import in another application) if accuracy is critical.

File seems corrupted or partially downloaded

Because CDX is binary, truncation or corruption often prevents opening and may produce opaque errors.

  1. Re-download or re-transfer the file (prefer a direct file transfer method rather than copy/paste through chat apps that may alter files).
  2. Ask the sender to export again (ideally also provide CDXML as an alternative).
  3. If you receive the same issue repeatedly, confirm the source application is saving CDX correctly by opening the file on the sender’s system.

FAQ

Is .CDX the same as CDXML?

They represent the same ChemDraw Exchange information in different encodings: CDX is tagged binary, while CDXML is an XML representation described as equivalent in the CDX/CDXML specification.

What is the internet media type (MIME type) for .CDX?

Sources such as the Library of Congress and Wolfram Language documentation list the internet media type as chemical/x-cdx.

Can Open Babel open .CDX files?

Open Babel’s documentation describes support for reading the ChemDraw binary format (.cdx), which can be used for import and conversion workflows.

Can I open .CDX on iPhone or Android?

Mobile platforms typically don’t provide reliable native CDX viewing/editing. The practical approach is to open or convert the file on a desktop CDX-capable tool and then view the converted result on mobile.

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