Full Featured ILS
Koha has all the modules you would expect to find in an integrated library management system - online public access catalog (OPAC), acquisitions, cataloging, serials, reporting, stock verification, patrons, system administration and a solid toolkit.
The OPAC catalog search is powered by the sophisticated Zebra search engine. Readers can view content from Google and Amazon. They can reserve books online, subscribe to RSS feeds, share reading lists and view fines, reading history and maintain their personal profile.
The acquisitions modules allows the staff to manage purchase suggestions, donations, budgets and orders.
Via the circulation module staff can issues and returns, inter-library loans and track reserve requests and overdue items.
The Serials module allows staff to track the delivery of serials and manage routing lists.
Via the System Administration screens staff can manage circulation rules, patron and item types, cataloging frameworks and more.
The tools section contains useful features including export or import, email notices, news label printing.
Completely Web Based
Both the Online Public Access Catalog (OPAC) and the staff client are completely web based. You don't need to install any software on the user's desktops. Web based system are much easier to manage during installs, software or hardware problems or upgrades.
Koha runs on all browsers including internet exlorer, Mozilla Firefox and Chrome.
Koha also runs windows, Linux and Mac based desktops.
Standards Compliant
Koha is compliant with various library standards like MARC21 for cataloging, Z39.50 for data exchange and SIP/NCIP for RFID based hardware.
Compliance to MARC21 standards makes it easy to migrate, import or export data from or to other library systems. Your publisher may supply MARC21 records that you can import into Koha.
With it's Z39.50 capabilities Koha can be made into a Z39.50 server, so others can search of copy records from your Koha installation. It goes without saying that Koha can consume records from other Z39.50 servers.
With SIP/NCIP compliance Koha becomes easy to integrate with RFID products from any vendor.
Z39.50 Copy Cataloging
You can use Koha's copy cataloging screen to search for and download MARC records from databases like the Library of Congress (LOC) database. There are over 400 such databases available from around the world.
This features saves classification and data entry effort and is particularly useful for libraries that don't have trained catalogers.
Library of Congress records are developed by professional catalogers, and contain detailed information about the material including abstract, subject, keywords, editions and more.
The search in the OPAC functions better as fields like subject and keyword provide more access points to Koha's search engine.
Patron Cards
You can print ready to use patron cards from Koha. Printing can be done in batches as well.
The card can include kind of information - patron number, name, address or expiry. It can also include a bar code to be used in circulation or patron modules.
The layout of the card - size, font, font size, colors, logo can be adjusted quite easily.
Federated Search
Koha includes a federated search engine called Pazpar2.
Pazpar2 can simultaneously search a set of Z39.50 or SRU/W compliant databases and produce a consolidated search result sorted by relevance.
With Pazpar2 it is possible to offer to patrons a simple Google like search screen that can query the Koha data for physical items and several free and paid electronic databases.
From the search results patrons can navigate directly to the content in the case of electronic material or to the description page on Koha in the case of physical items.
Off-line Circulation Tool
Koha includes a circulation tool for use during network or server unavailability.The tool needs to be installed on computers at the circulation desk. The tool stores stores circulation records in a file on the Desktop.
Once the server becomes available the file can be uploaded on Koha to synchronize the data.
Flexible Reporting
Koha has several pre-defined reports, from overdue reports to patron, acquisition or circulation statistics.

You can also design your own reports using the Guided Reports Wizard, here you can choose the report format, select data to be displayed in row or columns and set selection criteria.
For maximum flexibility you can write your own sql queries and run them directly from the user interface.
Reports data can be saved in text files. You can even schedule the reports to be run at pre-defined intervals.
Export and Import
Koha has excellent tools to import catalog, authorities or patron data.
If you are migrating a large no. of records you can use powerful command line tools. And if you need to import incremental records on an on-going basis you can use easy to use and flexible GUI tools.

Koha allows export of MARC data including biblios and holding in MARC or MARCXML formats.

Enhanced Content
Koha integrates with Google, Amazon and several other web services to display valuable content along with each catalog item.

Book jackets and previews from Google, or reader reviews and similar items lists from Amazon are very popular.
Koha is also able to group results by editions thanks to web services like XISBN.
Readers can also navigate seamlessly to other external database like Worldcat, Google Scholar or BookFinder.com if they need to.
Powerful Catalog Search
Zebra makes Koha's catalog search superior to commercial or open source alternatives.
Zebra can index and serve millions of records really fast.

You can search in any field - title, author, call no, subject and more, or search for a term in all fields at once. Zebra allows faceted search, sorting and drill down. You can create complex search conditions using AND and OR operators and the system is smart enough to find results for mis-spelled words!
Zebra is UTF-8 compliant, so your catalog records can be in any language.
Web 2.0 features
Koha supports several useful Web 2.0 features.
Use RSS feeds to get informed as new arrivals are added to the catalog.
You can create your own reading lists and share with friends. Library staff can create public reading lists to better serve their patrons.
Staff can publish News items on the OPAC or on the Staff Client for that matter.
We know patrons want to know what other readers think about a particular item. Patrons can submit comments on any item in the catalog. Staff can choose to moderate the comments before they are displayed on the OPAC.
Authority Control
You can create Author, Subject and other types of authority records.
When creating new records, catalogers can pick items from the authority files. This helps ensure consistency and high quality.
Multiple Libraries
With Koha you can setup multiple libraries on branches on the same system.
Patrons of one library can check-out and check-in items at any library.
Koha automatically setup up inter-library transfers.
Multi-Language
The Koha architecture support multi-language screens and catalog.
Due to the efforts of Koha contributors, Koha is available in several languages today including French, Arabic, Hindi, Taiwanese, Urdu and several others.
The Koha community also maintains collaborative translation tools on the web, so number of languages that Koha is available keeps increasing!
Bar coded Spine Labels
Koha comes pre-configured with commonly used layouts and templates. Or you can create your own.
You can search for and add a list of catalog items to be included in a printing batch.

Koha then generates a PDF file with the labels that printed off on any available printer.
Email Overdue & Other Notices
Koha can automatically email overdue or other notices to patrons.
Staff can setup content templates for events like overdues, the system then automatically populates details like patron name or card number and item details like title and author and generates the email.
Flexible Item Types & Digital Content
Koha comes pre-built with several useful item types - Books, Reference, Maps, DVD/CDs etc.

You can create their own item types as well. Once item types are set up you can use them and other attributes like patron type or library name to create granular circulation rules.
Koha can support digital content as well, all you need to do is to store the url of the electronic resource in tag 856 of the Marc record.
Stock-taking
Koha makes stock-taking simple. Library staff need to upload a file with items physically available in the library at a given time. This file can be generated by using bar code or RFID scanners.
Koha can then combine this data with information on items in circulation, or those that are withdrawn or damaged or lost to generate stock-taking reports including those on items that are missing.
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Fully RFID Ready
Koha is SIP & NCIP compliant and will work with any compliant RFID hardware. RFID can be used in circulation, stock-taking and security processes.
Z39.50 Database
You can expose your Koha catalog as a Z39.50 source. This way other libraries with Z39.50 compliant clients or Library Management Systems can copy your records with ease.