The fixed-H layerStep 12 of 17 of the InChI walkthrough. Merging tautomers is sometimes the wrong answer. The optional fixed-h layer pins the mobile hydrogens back onto specific atoms in an extra /f block, so the individual tautomers separate again. Standard InChI never emits it — this panel asks the engine for it explicitly, which is why the prologue here reads InChI=1 rather than InChI=1S.It opens on NC(N)=O, drawn live, so the layer under discussion changes as you change the structure.Convert a structure to its InChI and InChIKey and back, convert a whole CSV, XLSX or SDF file, learn how the identifier is derived, and practise writing its layers. The InChI engine is WebAssembly running in your browser, so the tool needs JavaScript — and nothing you open ever leaves your machine.

Convert — a structure in, an InChI out

Batch — a whole CSV, XLSX or SDF file

Tutorial — how an InChI is derived

Exercises — write the layers yourself

Cheatsheet — every layer in a table

Tests — the IUPAC regression corpora

Download — take the engine away

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