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ChemSema
Chemical drawing editor for structures, reaction schemes, ChemDraw file exchange, and editable Office documents.
Open source. 48 of 65 checklist features confirmed.
Main canvas
No dark mode
SDF import omits atom labels and overlaps bonds.
Default drawings
SDF rendered without atom labels; SMILES and MOL imports failed.
Caffeine
SDF rendered without atom labels and overlapped; SMILES and MOL imports failed.
Paclitaxel
No 3D view
Cholesterol in 3D
- Tested the hosted build in an isolated native WebKit host.
- SMILES and MOL files produced JSON parse errors; SDF files opened.
- SDF drawings projected 3D coordinates and omitted visible atom labels in WebKit.
- The fallback PNGs are crops of the test host window, not native exports.
- Save As downloaded the native CCJZ format.
Facts
- GitHub stars
- 6 stars on 6 Nov 2026
- First commit
- 15 Jun 2026
- Repository activity
- 609 commits, 2 contributors, last push 26 Sept 2026
- Latest version
- v1.0.0-beta.8
- Version we tested
- Web build 8e6f995 (2026-09-…
- Runs on
- Windows, Linux, Browser
- License
- Apache License 2.0; bundled components retain their own licenses.
- Price
- Free
- Relies on
- InChI. Ported into its own code: RDKit SMILES grammar. Custom editor; RDKit-derived SMILES grammar reimplemented in Rust; no RDKit runtime.
- Draws with
- Custom Rust render primitives rendered as SVG DOM/SVG files; Win32 GDI EMF; resvg/tiny-skia CLI PNG.
- Chemistry from
- In-house Rust chemistry; bundled IUPAC InChI 1.07.5.
- Interface
- JavaScript, HTML and CSS; Tauri 2/WebView2 on Windows.
- Main language
- Rust
- Other languages
- JavaScript: Editor interface and SVG DOM display; C: Bundled official InChI chemistry library
- Renderer
- Original: ChemSema molecular renderer
- Third-party licenses
- MIT InChI and BSD-3-Clause RDKit-derived code; Windows installer bundles proprietary Microsoft WebView2.
- Download
- 215 MB
- Beta; some architecture notes lag implemented multipage layout and Office write-back.
- Native desktop/OLE requires Windows; Linux is CLI-only; current source is newer than the released installer.
- Extended template libraries require assets from a locally licensed ChemDraw installation.
In use
Screenshots from our test of this version.
Features
- Tested by running it
- Seen in the app
- The manual says yes
- Partly, with the reason shown
- Not supported
- Not established, which is not the same as no
Select a mark for its proof. A filled mark opens our screenshot, or the manual if the check left nothing to picture. A ring opens the manual.
Drawing structures
- Partly: Drew all three orders; changing existing bonds not checked. Opens the cited page.Single, double and triple bondsDrew all three orders; changing existing bonds not checked.github.com
- Yes, tested by running it: Drew solid wedge, hashed wedge, and wavy bonds. Opens the screenshot.Wedge, hash and wavy bondsDrew solid wedge, hashed wedge, and wavy bonds.github.com
- Not establishedDative, hydrogen and quadruple bonds
- Yes, according to the manual. Opens the cited page.Choose double-bond sidegithub.com
- Yes, tested by running it: Benzene placed; ring sizes three through eight available. Opens the cited page.Ring toolsBenzene placed; ring sizes three through eight available.github.com
- Yes, according to the manual: Dedicated chair cyclohexane and flipped chair tools. Opens the cited page.Chair and Haworth ringsDedicated chair cyclohexane and flipped chair tools.github.com
- Yes, according to the manual. Opens the cited page.Chain toolgithub.com
- Partly: Chairs included; larger libraries require locally extracted ChemDraw assets. Opens the cited page.Template libraryChairs included; larger libraries require locally extracted ChemDraw assets.github.com
- Not establishedSave your own templates
- Yes, according to the manual. Opens the cited page.Group abbreviationsgithub.com
- Yes, according to the manual. Opens the cited page.Charges, isotopes and atom labelsgithub.com
- Yes, according to the manual. Opens the cited page.Radicals and lone pairsgithub.com
- Yes, according to the manual. Opens the cited page.Keyboard drawinggithub.com
- Yes, according to the manual: Freehand selection, rotation, flipping, and resizing. Opens the cited page.Lasso select and transformsFreehand selection, rotation, flipping, and resizing.github.com
- Not establishedTilt drawings in perspective
Reactions and mechanisms
- Yes, tested by running it: Drew forward and equilibrium arrows. Opens the cited page.Reaction arrowsDrew forward and equilibrium arrows.github.com
- Yes, tested by running it: Drew a curved arrow; half-head options visible. Opens the cited page.Curved mechanism arrowsDrew a curved arrow; half-head options visible.github.com
- Yes, according to the manual: Native scheme and step data retain reactants and products. Opens the cited page.Machine-readable reactionsNative scheme and step data retain reactants and products.github.com
- Yes, according to the manual: Manual mappings through Logical Objects JSON fields. Opens the cited page.Atom mappingManual mappings through Logical Objects JSON fields.github.com
- Yes, according to the manual. Opens the cited page.Orbitals and symbolsgithub.com
Figures and layout
- Yes, according to the manual. Opens the cited page.Rich text captionsgithub.com
- Yes, according to the manual. Opens the cited page.Shapes, brackets and curvesgithub.com
- Yes, according to the manual. Opens the cited page.Align and distributegithub.com
- Yes, according to the manual. Opens the cited page.Group and ungroupgithub.com
- Not established2D structure cleanup
- Yes, according to the manual: ACS Document 1996 preset. Opens the cited page.Journal drawing stylesACS Document 1996 preset.github.com
- Yes, according to the manual: Saved document defaults are restored by later editing commands. Opens the cited page.Reusable custom stylesSaved document defaults are restored by later editing commands.github.com
- Yes, according to the manual. Opens the cited page.Color controlgithub.com
- Yes, according to the manual: Highlight command adds colored atom circles and bond bands. Opens the cited page.Color highlightingHighlight command adds colored atom circles and bond bands.github.com
- Yes, according to the manual: Paper sizes, page counts, and automatic pagination. Opens the cited page.Page layout and multipagePaper sizes, page counts, and automatic pagination.github.com
- Yes, according to the manual. Opens the cited page.Imported picturesgithub.com
- Yes, according to the manual: Editable native TLC plates, gel plates, and tables. Opens the cited page.TLC plates and tablesEditable native TLC plates, gel plates, and tables.github.com
Chemistry intelligence
- Yes, according to the manual. Opens the cited page.Structure checkinggithub.com
- Partly: R/S from wedges; E/Z requires imported directional semantics. Opens the cited page.R/S and E/Z labelsR/S from wedges; E/Z requires imported directional semantics.github.com
- Yes, tested by running it: Caffeine selection showed C8H10N4O2 and formula weight 194.19. Opens the cited page.Formula and massCaffeine selection showed C8H10N4O2 and formula weight 194.19.github.com
- Not establishedProperty estimates
- No: No name-to-structure command found. Opens the cited page.Name to structureNo name-to-structure command found.
- No: Chemical property dialog requires a manually entered name. Opens the cited page.Structure to nameChemical property dialog requires a manually entered name.
- Yes, tested by running it: Generated a proton NMR spectrum for a drawn bond. Opens the cited page.NMR predictionGenerated a proton NMR spectrum for a drawn bond.github.com
- Yes, according to the manual: Editable element lists, generic lists, and atom-query properties. Opens the cited page.R-groups and query structuresEditable element lists, generic lists, and atom-query properties.github.com
- Yes, according to the manual: Native repeat semantics, attachments, crossing bonds, and repeat-unit expansion. Opens the cited page.Polymers and repeat unitsNative repeat semantics, attachments, crossing bonds, and repeat-unit expansion.github.com
- Not establishedPeptides and nucleic acids
- Not establishedImage to structure
- Not establishedOnline structure lookup
- No: No rotatable 3D view found. Opens the cited page.3D model viewNo rotatable 3D view found.
- Not establishedCrystal structures
Files and exchange
- Partly: Imported simple CDXML; Save As produced CCJZ. Opens the cited page.CDXML import and exportImported simple CDXML; Save As produced CCJZ.github.com
- Yes, according to the manual. Opens the cited page.CDX import and exportgithub.com
- Partly: SDF opened; MOL rejected; no MOL export found. Opens the cited page.MOL and SDFSDF opened; MOL rejected; no MOL export found.github.com
- Partly: SMILES copy command reported success; SMILES files failed to open. Opens the cited page.SMILESSMILES copy command reported success; SMILES files failed to open.github.com
- Yes, according to the manual: Local InChI/InChIKey generation; dative bonds rejected. Opens the cited page.InChILocal InChI/InChIKey generation; dative bonds rejected.github.com
- Not establishedRXN files
- Yes, according to the manual. Opens the cited page.SVG exportgithub.com
- Partly: PDF pages contain rasterized JPEG images, lacking vector artwork. Opens the cited page.PDF exportPDF pages contain rasterized JPEG images, lacking vector artwork.github.com
- Yes, according to the manual: CLI export supports adjustable scale and pixel dimensions. Opens the cited page.High-resolution PNGCLI export supports adjustable scale and pixel dimensions.github.com
- Partly: Editable paste from ChemDraw; reverse clipboard compatibility remains unverified. Opens the cited page.Paste to and from ChemDrawEditable paste from ChemDraw; reverse clipboard compatibility remains unverified.github.com
- Yes, according to the manual: Windows OLE objects support editing and storage write-back; beta. Opens the cited page.Editable in Word or PowerPointWindows OLE objects support editing and storage write-back; beta.github.com
- Yes, according to the manual: Windows OLE server supports embedded-object editing and storage write-back. Opens the cited page.Windows Office OLEWindows OLE server supports embedded-object editing and storage write-back.github.com
APIs and automation
- Not establishedPython API
- Yes, according to the manual: Typed WASM API loads documents, executes commands, and renders SVG. Opens the cited page.JavaScript or TypeScript APITyped WASM API loads documents, executes commands, and renders SVG.github.com
- Yes, according to the manual. Opens the cited page.Command-line toolgithub.com
- Yes, according to the manual: Documented agent CLI with selectors, bundles, transactions, and JSONL sessions. Opens the cited page.AI agent controlDocumented agent CLI with selectors, bundles, transactions, and JSONL sessions.github.com
- Not establishedBuilt-in AI assistant
Embedding and extension
- Not establishedPlugins
- Not established: Office OLE opens a separate editor; no embedded editor documented.Embed in your own appOffice OLE opens a separate editor; no embedded editor documented.github.com