GFF/GTF 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 2 specifications.

The GTF (General Transfer Format) is identical to GFF version 2.

• Fields
• Track lines
• More information

Fields

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. seqname - name of the chromosome or scaffold; chromosome names can be given with or without the 'chr' prefix. Important note: the seqname 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. feature - feature type name, e.g. Gene, Variation, Similarity
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. frame - 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. attribute - A semicolon-separated list of tag-value pairs, providing additional information about each feature.

Note that where the attributes contain identifiers that link the features together into a larger structure, these will be used by Ensembl to display the features as joined blocks.

Sample GTF output from Ensembl data dump:

  transcribed_unprocessed_pseudogene  gene          . + . gene_id "ENSG00000223972"; gene_name "DDX11L1"; gene_source "havana"; gene_biotype "transcribed_unprocessed_pseudogene";

  processed_transcript                transcript    . + . gene_id "ENSG00000223972"; transcript_id "ENST00000456328"; gene_name "DDX11L1"; gene_sourc e "havana"; gene_biotype "transcribed_unprocessed_pseudogene"; transcript_name "DDX11L1-002"; transcript_source "havana";

Sample GFF output from Ensembl export:

 X    Ensembl    Repeat                .    .    hid=trf; hstart=; hend=

 X    Ensembl    Repeat                -    .    hid=AluSx; hstart=; hend=

 X    Ensembl    Repeat                .    .    hid=dust; hstart=; hend=

 X    Ensembl    Pred.trans.            450.19    -        genscan=GENSCAN00000019335

 X    Ensembl    Variation            .    +    .

 X    Ensembl    Variation            .    +    .

Track lines

Although not part of the formal GFF specification, Ensembl uses track lines to further configure sets of features (thus maintaining compatibility with UCSC). Track lines should be placed at the beginning of the list of features they are to affect.

The track line consists of the word 'track' followed by space-separated key=value pairs - see the example below. Valid parameters used by Ensembl are:

• name - unique name to identify this track when parsing the file
• description - Label to be displayed under the track in Region in Detail
• priority - integer defining the order in which to display tracks, if multiple tracks are defined.

More information

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

Ensembl release 89 - May 2017 © EMBL-EBI