Data annotation is an essential process in machine learning (ML) that helps train and improves ML models’ accuracy. It involves identifying and labeling the data points or features used to train the model. This task can be tedious, but it’s essential for ensuring that the ML model performs accurately.
Several different data annotation tools are available, both commercial and open source. This article will explore the best data annotation tools available and guide choosing the right tool for your needs.

The Best Data Annotation Tool Types: Commercial, Open Source, and Freeware
Several different data annotation tools are available, each with its unique features. The following is a review of the most popular and effective data annotation tools, along with some guidance on how to choose the best tool for your needs:
Commercial Data Annotation Tools
Commercial data annotation tools are software packages that you purchase and install onto your computer from an online store or a CD/DVD. They require no special technical knowledge to use, but they can be more expensive than open-source or freeware alternatives.
In addition, they often come with limited documentation and require customer support for installation issues, leading to increased costs. Some commercial annotation tools do not offer discounts for academic institutions.
These would be classified as “for-profit” sources of data annotation tools, while others do, making it a more affordable option for academic researchers.
These tools offer a wide range of features, including data cleansing, pre-processing, and feature engineering. They also allow you to build custom models and algorithms and deploy them into production. However, they can be expensive and difficult to learn, so they may not suit everyone.
Benefits of Commercial Data Annotation Tools:
- Higher level of quality: Commercial data annotation tools are usually more user-friendly and offer a higher level of quality than open-source and freeware tools.
- Technical support: Commercial data annotation tools typically offer technical support, which can be helpful if you need assistance using the tool or troubleshooting errors.
- Feature-rich: Commercial data annotation tools often include various features, such as data cleaning, data transformation, and machine learning, that can be useful for ML models.
Drawbacks of Commercial Data Annotation Tools:
- Cost: Commercial data annotation tools are usually more expensive than open source and freeware tools.
- Limited functionality: Commercial data annotation tools may not include all the features you need for ML models.
- Complexity: Commercial data annotation tools can be more complex to use than open-source and freeware tools.
Open Source Data Annotation Tools
Open-source data annotation tools are software packages that are free to download and use. They often come with comprehensive documentation and a range of helpful tutorials, making them easy to get started with.
In addition, there are more open-source annotation tools available than commercial ones, which means that if one doesn’t meet your needs, you can switch to another. The main drawback is that the learning curve for these tools may be steeper, and they may not offer all the features of commercial data annotation tools.
Benefits of Open Source Data Annotation Tools:
- Free to use: Open source data annotation tools are free to use and often include various features.
- Technical expertise required: Open source data annotation tools typically require more technical expertise than commercial or freeware tools. This may be a disadvantage if you do not have the necessary skillset.
- Flexibility: Open source data annotation tools offer more flexibility than commercial and freeware tools, allowing you to customize them to your needs.
Drawbacks of Open Source Data Annotation Tools:
- Limited support: Open source data annotation tools may not have as much support as commercial or freeware tools.
- Limited functionality: Open source data annotation tools may not include all the features you need for ML models.
- Complexity: Open source data annotation tools can be more complex to use than commercial or freeware tools.
Freeware Data Annotation Tools
Freeware data annotation tools are packages that typically come as downloadable apps or executable files. They are very easy to use, but they often come with limited documentation and may not offer all the features of commercial or open-source tools.
Benefits of Freeware Data Annotation Tools:
- Free to use: Freeware data annotation tools are free to use and often include various features.
- No technical expertise required: Freeware data annotation tools do not typically require any technical expertise to use them. This can be helpful if you are not familiar with using software for data analysis and visualization.
- Widely used: Freeware data annotation tools, such as Microsoft Excel and Google Sheets, are widely used and can help communicate your data findings to others.
Drawbacks of Freeware Data Annotation Tools:
- Limited support: Freeware tools may not have as much support as commercial or open-source tools.
- Limited functionality: Freeware tools may not include all the features you need for ML models, such as data pre-processing and feature selection.
- Complexity: Freeware tools can be more complex to use than commercial or open-source tools since they do not offer any flexibility to customize them to your needs.
Iteration and Evolution: Changing Data Annotation Needs, New Tools
As your needs change over time, so can how you do any annotation.
Why change data annotation tools?
As your needs change, you may find that the tool you were using no longer meets your needs. This can be for several reasons, including:
- The tool is no longer supported or updated.
- It is difficult to learn and use.
- It does not offer all the features you need.
- You need more or fewer annotation features.
- Your research has changed, and the tool is no longer suitable.
How do I change data annotation tools?
If you decide that you need to switch to a different data annotation tool, there are several things you should do:
- Research your options and potential alternatives in detail.
- Identify which annotation tool will best meet your needs based on the feature requirements in your documentation and tutorials.
- Evaluate how much time it will take to learn the new data annotation tool and how much time it may save you in annotating future datasets compared to the previous tool.
- Check if any licenses or contracts need to be changed when you switch annotation tools so that you can avoid unexpected costs.
Questions to Ask Your Data Annotation Tool Provider
When deciding which data annotation tools to purchase, one must consider many factors, including quality, machine learning, and strategic approach. To make an informed decision, it is essential to ask your data annotation tool provider the following questions:
Strategic Approach
- What business goals do the toolset intend to help me achieve?
- How do I know if I’m using the tool correctly and getting the most value from it?
- What sort of return on investment (ROI) can I expect?
- How will my team be able to use the tool most effectively?
- Can you provide a proof of concept or a trial before purchase?
Key Features
- What features are included in the annotation toolset?
- Are all required features present, or do they need to be purchased as add-ons?
- Are features clearly explained in the documentation, or are they assumed to be well known?
- Do you offer other services like content moderation?
Quality
- How reliable is the annotation toolset?
- How much testing has been done on different datasets?
- What sort of support do you offer if my data is not annotated correctly or I run into errors when using the toolset?
Machine Learning
Currently, machine learning tools are relatively new, and their use cases are still being discovered. When choosing a data annotation tool that includes machine learning capabilities, consider these questions:
- How does this feature benefit me in real-life scenarios?
- How does it make life easier for me when doing annotations?
- What datasets can be used for machine learning?
- Can I see a demo of this feature in action?
- What type of support is available if I need help using the machine learning capabilities of the annotation tool?
- How much expertise do I need to use the machine learning capabilities effectively?
Conclusion
Choosing the right data annotation tool is an important decision that should not be taken lightly. By asking the right questions, you can ensure that you select a tool that meets your needs and helps you achieve your research goals.