This website is biased toward ReShiki, because its maintainer also maintains ReShiki. Please be careful.
Molbrett
A browser whiteboard for drawing chemical structures, synthetic routes, and annotated chemistry diagrams.
Free with paid plans. 39 of 65 checklist features confirmed.
Official demo
Main canvas
Black bonds have very low contrast on the dark canvas.
Default drawings
Caffeine
Paclitaxel
Cholesterol in 3D
- Molbrett main bundle identifier was 06dde1e7; embedded Ketcher About reports 3.18.0.
- SMILES layouts use colored heteroatoms and terminal carbon labels in the editor.
- SDF viewer defaults to lines on a gray background with explicit hydrogens.
- Chemical file download did not appear in the isolated WebKit host; SMILES previews were transcribed.
- RDKit canonicalized all three transcribed outputs identically to their fixture SMILES.
Facts
- Version we tested
- 06dde1e7
- Runs on
- Browser
- License
- Free cloud service; local deployment requires a license, free for academia.
- Price
- Free cloud; local academic licenses free; other local pricing by enquiry (2026-11-05).
- Plans
- Free cloud: $0 (2026-11-06); Local installation: Quote; free for academia (2026-11-06)
- Relies on
- Ketcher, Indigo. Embeds Ketcher with standalone Indigo chemistry; the surrounding whiteboard uses Excalidraw.
- Draws with
- Excalidraw HTML canvas whiteboard displaying SVG molecular images
- Chemistry from
- Indigo through embedded Ketcher standalone
- Interface
- React, Ketcher, and Excalidraw
- Main language
- TypeScript
- Other languages
- JavaScript: Molbrett UI and Miew 3D viewer; C++: Indigo chemistry compiled to WebAssembly
- Renderer
- Borrowed: Ketcher Raphael/SVG; whiteboard server undisclosed
- Third-party licenses
- MIT/Apache-2.0 components; DOMPurify also offers MPL-2.0; bundled Excalifont/Xiaolai fonts use OFL-1.1.
- Structures are edited in embedded Ketcher 3.18.0, separately from the diagram whiteboard.
- Macromolecule mode and image recognition are unavailable in this integration.
- Local installation is a licensed Docker server; vendor credentials are required.
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
- Yes, tested by running it: Drew single, double and triple bonds. Opens the cited page.Single, double and triple bondsDrew single, double and triple bonds.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
- Yes, according to the manual: Dative and hydrogen bonds in Ketcher. Opens the cited page.Dative, hydrogen and quadruple bondsDative and hydrogen bonds in Ketcher.github.com
- Not establishedChoose double-bond side
- Yes, tested by running it: Placed benzene; other ring sizes appear in the toolbar. Opens the screenshot.Ring toolsPlaced benzene; other ring sizes appear in the toolbar.github.com
- Not establishedChair and Haworth rings
- Yes, according to the manual: Dragging determines chain length in Ketcher. Opens the cited page.Chain toolDragging determines chain length in Ketcher.github.com
- Yes, tested by running it: Selected and placed adenine from the structure library. Opens the cited page.Template librarySelected and placed adenine from the structure library.github.com
- Yes, according to the manual: Ketcher saves drawings into its User Templates library. Opens the cited page.Save your own templatesKetcher saves drawings into its User Templates library.github.com
- Yes, according to the manual: Ketcher functional groups expand and contract chemically. Opens the cited page.Group abbreviationsKetcher functional groups expand and contract chemically.github.com
- Yes, according to the manual: Ketcher atom dialog includes label, alias, charge, and isotope. Opens the cited page.Charges, isotopes and atom labelsKetcher atom dialog includes label, alias, charge, and isotope.github.com
- Yes, according to the manual: Radical setting in Ketcher's atom properties. Opens the cited page.Radicals and lone pairsRadical setting in Ketcher's atom properties.github.com
- Yes, according to the manual: Click an atom and type its replacement label. Opens the cited page.Keyboard drawingClick an atom and type its replacement label.github.com
- Yes, according to the manual: Ketcher lasso/rotate/flip; whiteboard objects can be resized. Opens the cited page.Lasso select and transformsKetcher lasso/rotate/flip; whiteboard objects can be resized.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
- Partly: Drew a curved arrow; later editing was not checked. Opens the cited page.Curved mechanism arrowsDrew a curved arrow; later editing was not checked.
- Partly: Reaction drawing generated an RXN preview. Opens the cited page.Machine-readable reactionsReaction drawing generated an RXN preview.github.com
- Yes, according to the manual: Manual mapping, automatic mapping, and unmapping in Ketcher. Opens the cited page.Atom mappingManual mapping, automatic mapping, and unmapping in Ketcher.github.com
- Not establishedOrbitals and symbols
Figures and layout
- Partly: Whiteboard fonts supported; subscript/superscript formatting is confined to Ketcher. Opens the cited page.Rich text captionsWhiteboard fonts supported; subscript/superscript formatting is confined to Ketcher.github.com
- Yes, according to the manual: Excalidraw shapes, lines, and free drawing. Opens the cited page.Shapes, brackets and curvesExcalidraw shapes, lines, and free drawing.github.com
- Yes, according to the manual: Align selected whiteboard objects. Opens the cited page.Align and distributeAlign selected whiteboard objects.github.com
- Yes, according to the manual: Group and ungroup whiteboard objects. Opens the cited page.Group and ungroupGroup and ungroup whiteboard objects.github.com
- Yes, according to the manual: Ketcher normalizes bond lengths and angles. Opens the cited page.2D structure cleanupKetcher normalizes bond lengths and angles.github.com
- Partly: ACS preset applies in Ketcher, not to whiteboard styling. Opens the cited page.Journal drawing stylesACS preset applies in Ketcher, not to whiteboard styling.github.com
- Yes, seen in the app: Settings provide Save to File and Open from File. Opens the cited page.Reusable custom stylesSettings provide Save to File and Open from File.
- Yes, according to the manual: Selected whiteboard objects have individual stroke and fill colors. Opens the cited page.Color controlSelected whiteboard objects have individual stroke and fill colors.github.com
- Not establishedColor highlighting
- Not establishedPage layout and multipage
- Yes, according to the manual: Raster pictures on the Excalidraw whiteboard. Opens the cited page.Imported picturesRaster pictures on the Excalidraw whiteboard.github.com
- Not establishedTLC plates and tables
Chemistry intelligence
- Yes, according to the manual: Ketcher underlines invalid valences in red. Opens the cited page.Structure checkingKetcher underlines invalid valences in red.github.com
- Yes, according to the manual: Ketcher computes R/S, r/s, and E/Z descriptors. Opens the cited page.R/S and E/Z labelsKetcher computes R/S, r/s, and E/Z descriptors.github.com
- Yes, tested by running it: Caffeine: C8H10N4O2, molecular weight 194.194. Opens the cited page.Formula and massCaffeine: C8H10N4O2, molecular weight 194.194.github.com
- No: Calculated Values showed formula, masses and elemental analysis only. Opens the cited page.Property estimatesCalculated Values showed formula, masses and elemental analysis only.
- No: Entering caffeine in Open structure produced an editor error. Opens the cited page.Name to structureEntering caffeine in Open structure produced an editor error.
- No: No naming command found in editor controls or save formats. Opens the cited page.Structure to nameNo naming command found in editor controls or save formats.
- Not establishedNMR prediction
- Yes, according to the manual: Ketcher supports R-groups, atom lists, and attachment logic. Opens the cited page.R-groups and query structuresKetcher supports R-groups, atom lists, and attachment logic.github.com
- Yes, according to the manual: Ketcher SRU polymers and copolymer S-groups. Opens the cited page.Polymers and repeat unitsKetcher SRU polymers and copolymer S-groups.github.com
- No: Dedicated macromolecule authoring is explicitly disabled. Opens the cited page.Peptides and nucleic acidsDedicated macromolecule authoring is explicitly disabled.molbrett.elsci.io
- No: Recognition explicitly unsupported in the embedded standalone service. Opens the cited page.Image to structureRecognition explicitly unsupported in the embedded standalone service.github.com
- Not establishedOnline structure lookup
- Yes, tested by running it: SDF model rotated in depth; SMILES model was flat. Opens the screenshot.3D model viewSDF model rotated in depth; SMILES model was flat.github.com
- Not establishedCrystal structures
Files and exchange
- Partly: Generated CDXML preview reimported; file download failed in host. Opens the cited page.CDXML import and exportGenerated CDXML preview reimported; file download failed in host.github.com
- Yes, according to the manual: Structure import/export through Ketcher; whiteboards use Excalidraw format. Opens the cited page.CDX import and exportStructure import/export through Ketcher; whiteboards use Excalidraw format.github.com
- Partly: MOL and SDF opened; MOL preview generated, download absent. Opens the cited page.MOL and SDFMOL and SDF opened; MOL preview generated, download absent.github.com
- Yes, tested by running it: SMILES imported and output previews generated for three fixtures. Opens the cited page.SMILESSMILES imported and output previews generated for three fixtures.github.com
- Yes, according to the manual: Paste InChI directly onto the whiteboard. Opens the cited page.InChIPaste InChI directly onto the whiteboard.elsci.io
- Partly: RXN preview generated for a drawing with arrows. Opens the cited page.RXN filesRXN preview generated for a drawing with arrows.github.com
- Yes, tested by running it: Board SVG downloads generated for all three fixtures. Opens the cited page.SVG exportBoard SVG downloads generated for all three fixtures.github.com
- No: Board export offered PNG and SVG, with no PDF option. Opens the cited page.PDF exportBoard export offered PNG and SVG, with no PDF option.
- Partly: Default 2× PNG exported; no DPI control was shown. Opens the screenshot.High-resolution PNGDefault 2× PNG exported; no DPI control was shown.
- Not establishedPaste to and from ChemDraw
- Not establishedEditable in Word or PowerPoint
- Not establishedWindows Office OLE
APIs and automation
- Not establishedPython API
- Not establishedJavaScript or TypeScript API
- Not establishedCommand-line tool
- Not establishedAI agent control
- Not establishedBuilt-in AI assistant
Embedding and extension
- Not establishedPlugins
- No: Hosted X-Frame-Options DENY; no alternative embed route documented. Opens the cited page.Embed in your own appHosted X-Frame-Options DENY; no alternative embed route documented.molbrett.elsci.io