.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: 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 .CDX files

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

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).
Right-click the .cdx file → Open with → choose the installed CDX-capable app.
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

Open the .cdx file in a CDX-capable chemistry tool (commonly ChemDraw; alternatively, use Wolfram Language Import, or convert via Open Babel).
Control-click the file → Open With → select the app (use “Other…” if it’s not listed).
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

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).
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).
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

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

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.

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

Norton 360 delivers comprehensive antivirus protection, VPN, and identity theft monitoring. Scan files for threats before opening to keep your device secure.

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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

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

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.

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

Try converting to CDXML first (the specification describes CDX↔CDXML equivalence), then convert from CDXML to your target format if needed.
If possible, open the file in ChemDraw and export to the exact target format you need.
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.

Re-download or re-transfer the file (prefer a direct file transfer method rather than copy/paste through chat apps that may alter files).
Ask the sender to export again (ideally also provide CDXML as an alternative).
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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