### 16.3. Are there any technical limitations for InChI input? 

Yes, there are. Some of them follow.

1)      InChI input may not contain more than 1023 atoms.

2)      Not more than 20 bonds per atom are allowed.

3)      Allowed bond types are single, double, and triple. As an exception, "aromatic bonds" are also allowed only to be immediately converted into alternating single/double bonds by the InChI Software. Since this conversion is not bulletproof at all (partially because a formal definition of aromatic bonds accepted by everybody does not exist) the use of  aromatic bonds is strongly discouraged.

Since v. 1.05, InChI software includes experimental support of ‘large’ molecules containing up to 32767 atoms (for Molfile input, V3000 format is necessary).