GFF3 File Format - Definition and supported options

The GFF (General Feature Format) format consists of one line per feature, each containing 9 columns of data, plus optional track definition lines. The following documentation is based on the Version 3 specifications.


The first line of a GFF3 file must be a comment that identifies the version, e.g.

##gff-version 3

Fields must be tab-separated. Also, all but the final field in each feature line must contain a value; "empty" columns should be denoted with a '.'

  1. seqid - name of the chromosome or scaffold; chromosome names can be given with or without the 'chr' prefix. Important note: the seq ID must be one used within Ensembl, i.e. a standard chromosome name or an Ensembl identifier such as a scaffold ID, without any additional content such as species or assembly. See the example GFF output below.
  2. source - name of the program that generated this feature, or the data source (database or project name)
  3. type - type of feature. Must be a term or accession from the SOFA sequence ontology
  4. start - Start position of the feature, with sequence numbering starting at 1.
  5. end - End position of the feature, with sequence numbering starting at 1.
  6. score - A floating point value.
  7. strand - defined as + (forward) or - (reverse).
  8. phase - One of '0', '1' or '2'. '0' indicates that the first base of the feature is the first base of a codon, '1' that the second base is the first base of a codon, and so on..
  9. attributes - A semicolon-separated list of tag-value pairs, providing additional information about each feature. Some of these tags are predefined, e.g. ID, Name, Alias, Parent - see the GFF documentation for more details.

Note that where the attributes contain Parent identifiers, these will be used by Ensembl to display the features as joined blocks.

##gff-version 3
ctg123 . mRNA            1300  9000  .  +  .  ID=mrna0001;Name=sonichedgehog
ctg123 . exon            1300  1500  .  +  .  ID=exon00001;Parent=mrna0001
ctg123 . exon            1050  1500  .  +  .  ID=exon00002;Parent=mrna0001
ctg123 . exon            3000  3902  .  +  .  ID=exon00003;Parent=mrna0001
ctg123 . exon            5000  5500  .  +  .  ID=exon00004;Parent=mrna0001
ctg123 . exon            7000  9000  .  +  .  ID=exon00005;Parent=mrna0001

More information

For more information about this file format, see the documentation on the GMOD wiki.