What are the key differences between VCF versions 4.1 and 4.2? It looks like v4.3 contains a changelog (specs available here) but earlier specifications do not. This biostar post points out one difference: the introduction of Number=R for fields with one value per allele including REF  can anyone enumerate the other changes between these two versions?
What's the difference between VCF spec versions 4.1 and 4.2?
vcf;htslib;file formats
This is easy to check, you can download both specs in .tex format and do diff.Changes to the v4.2 compared to v4.1:Information field format: adding source and version as recommended fields.INFO field can have one value for each possible allele (code R).For all of the ##INFO, ##FORMAT, ##FILTER, and ##ALT metainformation, extra fields can be included after the default fields.Alternate base (ALT) can include *: missing due to a upstream deletion.Quality scores, a sentence removed: High QUAL scores indicate high confidence calls. Although traditionally people use integer phred scores, this field is permitted to be a floating point to enable higher resolution for low confidence calls if desired.Examples changed a bit.