What Are CAT Tools? A Guide to Computer-Assisted Translation

A CAT tool — short for computer-assisted translation tool — is software that helps a human translator work faster and more consistently. Crucially, a CAT tool does not translate text for you. A person does the translating; the software supports them with features like translation memory, glossaries, and automated quality checks. CAT tools are the everyday workhorses of the professional translation industry.

The name causes occasional confusion — it has nothing to do with cats. The "CAT" stands for computer-assisted (sometimes computer-aided) translation, and the category sits at the heart of how modern translation actually gets done.

What is computer-assisted translation?

Computer-assisted translation is an approach in which a human translator does the work of translating, but software handles the repetitive and error-prone parts around it. This is fundamentally different from machine translation, where software produces the translation automatically. With a CAT tool, the human stays in control of meaning and quality, and the computer makes them more productive.

A CAT tool typically breaks a document into small chunks called segments — usually sentences — and presents them in a two-column editor, with the source text on one side and space for the translation on the other. As the translator works through the segments, the tool quietly does several useful things in the background: remembering past translations, enforcing approved terminology, and flagging likely mistakes.

Key features of CAT tools

Different CAT tools vary, but most share a core set of features that define the category.

• Translation memory (TM). This is the heart of a CAT tool. Every segment you translate is stored in a database alongside its source. When an identical or similar sentence appears again — in the same document or a future project — the tool automatically suggests your previous translation. Over time this builds a valuable, reusable asset that saves enormous effort on repetitive content and keeps your wording consistent.
• Fuzzy matching. When a new sentence is similar but not identical to one in the translation memory, the tool shows the closest match and highlights the differences, so you only need to adjust what changed rather than translate from scratch.
• Terminology management (glossaries). CAT tools let you maintain a glossary of approved terms — product names, technical vocabulary, client-preferred wording — and prompt you to use them consistently. This is essential for brand and technical accuracy across a large project.
• Quality assurance (QA) checks. Automated checks catch common errors: inconsistent translations, missing numbers, broken formatting tags, double spaces, and untranslated segments.
• File format support. Good CAT tools can import many file types — Word documents, spreadsheets, web and software files, subtitle files, and more — let you translate just the text while protecting the formatting, then export the file back in its original format.
• Machine translation integration. Most modern CAT tools can plug in a machine translation engine such as DeepL or Google Translate to suggest a draft for each segment, which the translator then edits — a workflow known as post-editing.

CAT tools vs. machine translation

It is easy to confuse the two, but they play different roles. A CAT tool is an environment for a human translator, built around reusing that human's own work. Machine translation is an automatic process that generates a translation with no human involvement. The difference matters: machine translation answers "what does this say in another language?" instantly but imperfectly, while a CAT tool helps a professional produce a polished, consistent, human-quality translation efficiently.

In practice, the two increasingly work together. Machine translation is now built into most CAT tools as a productivity feature, offering a first-draft suggestion for each segment that the translator refines. The human remains responsible for the final quality — which is exactly the point. For a deeper look at where each approach fits, see our guide to human vs. machine translation.

CAT tools vs. translation management systems (TMS)

Another common source of confusion is the difference between a CAT tool and a translation management system, or TMS. They are related but solve different problems.

A CAT tool is where translation actually happens — the translator's editing workspace, centered on translation memory and terminology. Its job is to make the act of translating faster and more consistent.

A translation management system is broader. It is project- and workflow-management software for translation: it handles uploading and assigning files, managing translators and reviewers, tracking deadlines and status, and coordinating large volumes of work across many languages. A TMS is about managing the process; a CAT tool is about doing the translation.

The line between them has blurred. Many modern platforms bundle a CAT editor inside a larger management system, so a single product offers both the translation workspace and the project coordination around it. But the conceptual distinction is worth keeping clear: if you are translating, you are using the CAT part; if you are assigning, tracking, and delivering jobs, you are using the TMS part.

Who uses CAT tools, and why?

CAT tools are standard equipment for professional translators and the language service providers who employ them. A few reasons they are so widely adopted:

• Consistency. Translation memory and glossaries ensure the same phrase is translated the same way every time — vital for technical, legal, and branded content.
• Efficiency. Reusing past translations dramatically speeds up repetitive work, such as updated versions of a manual or a product catalogue.
• Collaboration. Shared translation memories and glossaries let teams of translators work consistently on the same large project.
• Cost savings. Because repeated content can be reused, clients often pay less for it — and many agencies require translators to use a CAT tool precisely so that these efficiencies can be measured and shared.

For these reasons, owning and knowing a CAT tool is often a baseline expectation for working as a professional translator, much as proficiency with translation itself. (If you are new to the broader subject, our explainer on what translation is is a good starting point.)

Examples of CAT tools

The CAT tool landscape ranges from free, open-source software to premium professional suites. In our resource directory we review the leading options in depth, including:

• OmegaT — a free, open-source CAT tool that provides translation memory, glossaries, and broad file support. It is the natural starting point for translators who want professional features without a license cost.
• Trados Studio — the long-standing industry standard, a comprehensive professional environment widely required by agencies, with powerful translation-memory and terminology capabilities.

Other well-known names include memoQ, Phrase, and Smartcat, several of which now combine a CAT editor with broader management features and AI assistance.

The bottom line

CAT tools are the quiet infrastructure of professional translation. They do not replace the translator — they amplify one, turning translation from a fully manual task into a faster, more consistent, and more collaborative one through translation memory, glossaries, and quality checks. Whether you are considering a career in translation, buying translation services, or simply curious how the industry works, understanding CAT tools is understanding how modern translation gets done. To explore specific options, browse our directory of translation resources.