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CRF++

taku910.github.io/crfpp Developer Tools Online tool

The CRF++ toolkit implements Conditional Random Fields for segmenting and labeling sequential data in natural language processing tasks.

Visit CRF++ 24 alternatives
taku910.github.io/crfpp
CRF++ homepage screenshot

About CRF++

CRF++ is a C++ toolkit for training and applying Conditional Random Fields (CRFs), a statistical method for segmenting and labeling sequential data. The homepage names named entity recognition, information extraction and text chunking as example natural language processing tasks it is designed for.

Training and test files must follow a fixed format. Each token sits on its own line with whitespace-separated columns, the last column holds the correct answer tag, and a blank line separates sentences. The homepage lists a binary package for MS-Windows and source installation through configure and make, which requires a C++ compiler (gcc 3.0 or higher). The most recent release listed on the homepage is version 0.58, released 2013-02-13.

Key features

  • Lets users redefine feature sets through feature templates
  • Training based on LBFGS, a quasi-Newton optimization algorithm
  • Outputs n-best results and marginal probabilities for all candidates
  • Supports single-best MIRA training
  • Provides Perl, Ruby, Python and Java bindings
  • Written in C++ with STL, with a C++ API for applications
Best for: Researchers and developers building natural language processing systems for sequence labeling tasks, such as named entity recognition or text chunking, who are comfortable building software from source or using a Windows binary.
Good for
  • The homepage describes fast training and lower memory use in both training and testing.
  • The homepage describes it as free software, released under the GNU LGPL or new BSD license.
  • Language bindings are available for Perl, Ruby, Python and Java.
Watch out for
  • Training and test files must use a fixed number of columns for all tokens.
  • Building from source requires a C++ compiler, with gcc 3.0 or higher listed as the requirement.
  • The homepage lists a prebuilt binary package only for MS-Windows.

CRF++ at a glance

Type
Online tool
Pricing
Not confirmed. Check the site
Platforms
Web, Windows
Open source
Not stated
Last checked
Oct 6, 2026 · Online when checked
Listed
Oct 5, 2026
developer tools

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CRF++ FAQ

What input format does CRF++ expect?
Each token goes on its own line, with columns separated by spaces or tab characters. The last column holds the true answer tag, and an empty line marks the boundary between sentences. The number of columns must be the same for every token.
What license is CRF++ released under?
The homepage states that CRF++ is free software that can be redistributed and modified under the terms of the GNU Lesser General Public License or the new BSD License.
Does the author ask users to report their use of the software?
Yes. The homepage asks users who use CRF++ for research, or who find research publications that apply it, to let the author know.
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Listing maintained by Chris McClure and the WebIndexly editors · Updated Oct 12, 2026 · How we rank