Bonds snap to chemistry
New bonds land on real bond angles: 120° zigzags, linear triple bonds and allenes, the free side of a ring atom. Rings fuse onto the bond you point at.
ChemSketch Freeware is gone. Draw in the browser instead
In 2026 ACD/Labs became part of Revvity Signals, the maker of ChemDraw, and ChemSketch Freeware was discontinued. Covalent is free and runs in any modern browser on Windows, macOS, Linux, Chromebooks and tablets, with the chemistry checked as you draw.
ChemSketch compared with Covalent
| What you need | ChemSketch | Covalent |
|---|---|---|
| Price | Freeware discontinued, no longer sold to new customers | Free |
| Installation | Windows program | None, runs in the browser |
| macOS, Linux, Chromebook, tablet | No | Yes |
| Bond, ring and chain tools | Yes | Yes |
| Wedged and hashed bonds | Yes | Yes |
| Valence check | Check Structure command | Refuses as you draw |
| Read SMILES and MOL files | Yes | Yes |
| Export MOL and images | Yes | MOL, SVG and PNG |
| Formula and molar mass | Yes | Live, while you draw |
| 3D model | ACD/3D Viewer | Ball and stick, sticks, space filling |
| Reaction arrows and conditions | Yes | With reaction SMILES and RXN files |
| Pages with structures and text | Yes | Yes |
| Templates | Rings, glassware and biomolecules | Worksheet, exam, reaction scheme, group meeting |
| PDF and print | Yes | Yes |
| Structure to IUPAC name | Yes | Shows the name for catalogued compounds |
ChemSketch still does things Covalent does not: glassware and orbital drawings, a large template library, polymer and biomolecule tools and ACD's property predictions. A copy that is installed keeps working; Covalent is for the computers and people that can no longer get one.
What Covalent does differently
Impossible structures are refused
A fifth bond to carbon or a double bond to a saturated nitrogen is stopped as you draw, with a plain explanation, instead of producing a structure no chemist can make.
Stereochemistry that round-trips
Wedges and hashes are read the way RDKit and the InChI library read them, and a structure opened from SMILES comes back with its stereocentres drawn.
Every compound in the database
Insert any of 48,000 compounds by name, CAS number or formula, or paste SMILES or a MOL block straight onto the canvas.
Whole documents, not just drawings
Lay out structures, text, arrows and answer lines on pages, start from a worksheet, exam, reaction scheme or group-meeting template, switch the whole document to ACS 1996 and download a PDF or paste it into Google Docs.
Common questions
Can I still download ChemSketch Freeware?
No. ACD/Labs lists ChemSketch Freeware as discontinued and points to a ChemDraw trial instead, and ChemSketch is no longer sold to new customers.
Can I bring my ChemSketch drawings?
Not the .sk2 files themselves. Save the structures from ChemSketch as MOL files and open those in Covalent, or copy SMILES and paste them onto the canvas.
Does Covalent run on a Mac?
Yes. ChemSketch was a Windows program; Covalent runs in Safari, Chrome or Firefox on a Mac, and on Linux and Chromebooks too.