What are CAT tools and why we love them so much

Computer-assisted translation tools – or CAT tools – are the omnipresent software for nearly every translator, reviewer, project manager, or anyone involved in the translation and localization industry. They’ve been increasing productivity and word per hour output rates since the early 1990’s, when the industry-leader Trados – called Translators Workbench at the time – was released.

Older translators might remember translating with a cat on their laps rather than a CAT tool on their computers, but knowledge of these tools has been nothing less than mandatory for younger and not-so-younger generations of linguists entering the market. I first heard about Trados on the very first day of my very first internship, back in 2008, and I’ve rarely worked without some sort of assistance ever since.

Whether you’re interested in a career in translation, need to know how your employees work, or are just curious to know how your language vendor is able to deliver so many languages with so much quality in so little time, here’s a basic guide on how CAT tools work and why they’re our best friends.

In this article:

Basic functionality of CAT tools

Like other professional software (video editors, word processors, spreadsheets etc.), CAT tools come in all different flavors, but they all function more or less the same way.

A CAT tool separates a text document into segments, leaving a blank editor next to each one where they can be translated. The translator then inputs their translation into these segments, and the program saves each translated segment into a translation memory, a database of bilingual strings of text. Whenever the translator runs into a similar string, the software then retrieves and displays the previously translated string, and all the translator needs to do is review and edit it, if needed.

Example from the Smartcat CAT tool
Example from the Smartcat editor

Desktop x cloud CAT tools

The first CAT tools were offline-only, meaning that you’d receive a compatible file from your client or agency, work on it in the tool, export it and send it back. You needed to have the software installed on your computer and stay on top of updates. There are still advantages to working like this, mainly for security reasons, but today most companies are migrating to cloud-based software.

Using a cloud-based tool means everyone on your team can use it, regardless of operational system, as it can be accessed from a web browser. This also makes it easier to share translation memories and glossaries in real time, maintaining consistency across the entire team. These tools also tend to be on the less expensive side.

Don’t confuse CAT tools with automatic translation

When you hear “translation software”, it’s not hard to immediately think of AI automatic translators such as Google Translate or Deepl. Although this can be a functionality of some CAT tools and has its place, it’s a very small part of how these tools actually help the translation workflow.

A CAT tool stores and retrieves pieces of human translation to improve consistency, minimize errors and increase speed. An automatic translator converts text using artificial intelligence and machine learning algorithms.

Main features of CAT tools

Let’s dig a little deeper on the main features that make up a CAT tool and what makes them so helpful.

Translation memory

Commonly referred to as TM, the translation memory forms the core of a CAT tool’s functionality. It’s the database that stores all the bilingual segments of text.

The tool compares each new segment to the segments it finds stored in the TM, then gives it a percentage match, that is, how much this new segment is similar to any previously saved segment. If the match is close to 100%, the tool automatically copies it to the editor and the translator can choose to edit it or quickly move on to the next segment. These percentages are highly customizable, and similar segments are often called fuzzy matches.


The glossary, or term base, is a smaller version of a TM, but instead of entire segments, it stores important terms defined by the user, along with their translations. Whenever a glossary term appears on a segment, the tool highlights it and shows its translation. It’s incredibly helpful to keep documents consistent over time and across team members.

Quality assurance (QA) check

Also with highly customizable parameters, the tool can check for several quality issues, including grammar and spelling errors, missing punctuation, wrong numbers, blocklisted terms, and even misplaced formatting tags. It’s not magical, though: it won’t check for readability or style.

Machine translation

As I mentioned before, machine translation, or MT, can be a very useful tool in a translation process. Most CAT tools allow integration with automatic translators via APIs. When this is enabled, you can customize the tool so that it automatically translates each new segment, and all you have to do is review and save it.

In the translation industry, this process is called machine translation post-edit, or MTPE, but that’s a story for another time.

Translation Management System

Most modern, cloud-based CAT tools have evolved to become a Translation Management System, or TMS, with an integrated translation editor. These systems allow project managers to easily assign tasks to different linguists, in different languages, and over different stages of the translation workflow. They can also follow up on task completion, and linguists can leave comments and efficiently communicate issues. This greatly speeds up the entire process and reduces human error significantly.

Current state of the market

According to a 2022 article by Redokun, SDL Trados still reigns supreme as the most popular CAT tool. Not surprisingly, it’s also rated the least favorite by translators. After that, the most commonly used tools are Wordfast and MemoQ. But these are far from being the only options. New tools are constantly being released, including proprietary software from clients and agencies.

And that trend doesn’t seem to be anywhere near the end. Adoption of translation software is almost unanimous. ​​The study shows that 88% of full-time professional translators use at least one CAT tool, and out of them, 76% used more than one. For companies, Business Insider reports a 90% reduction in translation costs stemming from human errors, unnecessary email communication, and time spent on uploading content and searching databases.

Further reading

I hope this article left you with a general understanding of what CAT tools are and how helpful they can be for clients, project managers and translators alike. If you’d like to get more in-depth information, check out these resources:

About Author

I'm a translator and writer with 15 years of experience in the tech localization industry. Former Brazilian Portuguese Review Quality Coordinator on contract for Google, I now provide high-end translation and writing services to quality-centered clients. I'm currently studying JavaScript and front-end development.