tabix.1

.TH tabix 1 "27 October 2026" "htslib-1.25" "Bioinformatics tools"
.SH NAME
.PP
tabix \- Generic indexer for TAB-delimited genome position files
.\"
.\" Copyright (C) 2009-2011 Broad Institute.
.\" Copyright (C) 2014, 2016, 2018, 2020, 2022, 2024, 2026 Genome Research Ltd.
.\"
.\" Author: Heng Li <lh3@sanger.ac.uk>
.\"
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.SH SYNOPSIS
.PP
.B tabix
.RB [ -0lf ]
.RB [ -p
gff|bed|sam|vcf]
.RB [ -s
.IR seqCol ]
.RB [ -b
.IR begCol ]
.RB [ -e
.IR endCol ]
.RB [ -S
.IR lineSkip ]
.RB [ -c
.IR metaChar ]
.I in.tab.bgz
.RI [ "region1 " [ "region2 " [ ... "]]]"

.SH DESCRIPTION
.PP
Tabix indexes a TAB-delimited genome position file
.I in.tab.bgz
and creates an index file
.RI ( in.tab.bgz.tbi
or 
.IR in.tab.bgz.csi )
when
.I region
is absent from the command-line. The input data file must be position
sorted and compressed by
.B bgzip
which has a
.BR gzip (1)
like interface.

After indexing, tabix is able to quickly retrieve data lines overlapping
.I regions
specified in the format "chr:beginPos-endPos".
(Coordinates specified in this region format are 1-based and inclusive.)

Fast data retrieval also
works over network if URI is given as a file name and in this case the
index file will be downloaded if it is not present locally.

The tabix
.RI ( .tbi )
and BAI index formats can handle individual chromosomes up to 512 Mbp
(2^29 bases) in length.
If your input file might contain data lines with begin or end positions
greater than that, you will need to use a CSI index.

Multiple threads can be used for operations except listing of sequence names.

.SH INDEXING OPTIONS
.TP 10
.B -0, --zero-based
Specify that the position in the data file is 0-based half-open
(e.g. UCSC files) rather than 1-based.
.TP
.BI "-b, --begin " INT
Column of start chromosomal position.
.TP
.BI "-c, --comment " CHAR
Skip lines started with character CHAR.
.TP
.BI "-C, --csi"
Produce CSI format index instead of classical tabix or BAI style indices.
.TP
.BI "-e, --end " INT
Column of end chromosomal position. The end column can be the same as the
start column.
.TP
.B "-f, --force "
Force to overwrite the index file if it is present.
.TP
.BI "-m, --min-shift " INT
Set minimal interval size for CSI indices to 2^INT [14]
.TP
.BI "-p, --preset " STR
Input format for indexing. Valid values are: gff, bed, sam, vcf.
This option should not be applied together with any of
.BR -s ", " -b ", " -e ", " -c " and " -0 ;
it is not used for data retrieval because this setting is stored in
the index file.
.TP
.BI "-s, --sequence " INT
Column of sequence name. Option
.BR -s ", " -b ", " -e ", " -S ", " -c " and " -0
are all stored in the index file and thus not used in data retrieval.
.TP
.BI "-S, --skip-lines " INT
Skip first INT lines in the data file.

.SH QUERYING AND OTHER OPTIONS
.TP
.B "-h, --print-header "
Print also the header/meta lines.
.TP
.B "-H, --only-header "
Print only the header/meta lines.
.TP
.B "-l, --list-chroms "
List the sequence names stored in the index file.
.TP
.BI "-r, --reheader " FILE
Replace the header with the content of FILE
.TP
.BI "-R, --regions " FILE
Restrict to regions listed in the FILE. The FILE can be BED file (requires .bed, .bed.gz, .bed.bgz 
file name extension) or a TAB-delimited file with CHROM, POS, and,  optionally,
POS_TO columns, where positions are 1-based and inclusive.  When this option is in use, the input
file may not be sorted. 
.TP
.BI "-T, --targets " FILE
Similar to 
.B -R
but the entire input will be read sequentially and regions not listed in FILE will be skipped.
.TP
.B "-u, --unique"
Only print output lines once,
even if they are covered more than once in the regions list.

This option cannot be used with
.B --separate-regions.
.TP
.BI "-D "
Do not download the index file before opening it. Valid for remote files only.
.TP
.BI "--cache " INT
Set the BGZF block cache size to INT megabytes. [10]

This is of most benefit when the
.B -R
option is used, which can cause blocks to be read more than once.
Setting the size to 0 will disable the cache.
.TP
.B --separate-regions
This option can be used when multiple regions are supplied in the command line
and the user needs to quickly see which file records belong to which region.
For this, a line with the name of the region, preceded by the file specific
comment symbol, is inserted in the output before its corresponding group of
records.

This option cannot be used with
.B --unique.
.TP
.BI "--verbosity " INT
Set verbosity of logging messages printed to stderr.
The default is 3, which turns on error and warning messages;
2 reduces warning messages;
1 prints only error messages and 0 is mostly silent.
Values higher than 3 produce additional informational and debugging messages.
.TP
.BI "-@, --threads " INT
Set number of threads to use for the operation.
The default is 0, where no extra threads are in use.
.PP
Unless one of the options
.BR -0 ,
.BR -b ,
.BR -c ,
.BR -e ,
.BR -p ,
.BR -s ,
or
.B -S
is used when building an index,
tabix will attempt to set its configuration by detecting the file type being
indexed.
If detection fails, or any of the options above is present,
the settings used will be those for the gff preset unless overridden
.br
i.e. one-based positions,
.B -s 1 -b 4 -e 5 -c '#' -S 0

.PP
.SH EXAMPLE
(grep "^#" in.gff; grep -v "^#" in.gff | sort -t"`printf '\(rst'`" -k1,1 -k4,4n) | bgzip > sorted.gff.gz;

tabix -p gff sorted.gff.gz;

tabix sorted.gff.gz chr1:10,000,000-20,000,000;

.SH NOTES
It is straightforward to achieve overlap queries using the standard
B-tree index (with or without binning) implemented in all SQL databases,
or the R-tree index in PostgreSQL and Oracle. But there are still many
reasons to use tabix. Firstly, tabix directly works with a lot of widely
used TAB-delimited formats such as GFF/GTF and BED. We do not need to
design database schema or specialized binary formats. Data do not need
to be duplicated in different formats, either. Secondly, tabix works on
compressed data files while most SQL databases do not. The GenCode
annotation GTF can be compressed down to 4%.  Thirdly, tabix is
fast. The same indexing algorithm is known to work efficiently for an
alignment with a few billion short reads. SQL databases probably cannot
easily handle data at this scale. Last but not the least, tabix supports
remote data retrieval. One can put the data file and the index at an FTP
or HTTP server, and other users or even web services will be able to get
a slice without downloading the entire file.

.SH AUTHOR
.PP
Tabix was written by Heng Li. The BGZF library was originally
implemented by Bob Handsaker and modified by Heng Li for remote file
access and in-memory caching.

.SH SEE ALSO
.IR bgzip (1),
.IR samtools (1)