SVGO and manual XML checks

Before publishing SVG, you may use an optimization tool such as SVGO.

This is done to reduce unnecessary attributes, comments, and metadata, and to make the file smaller.

This is useful work.

However, in anonymity checks, you cannot say "it is safe because it went through SVGO." The information the tool removes and the information a human must look at are different.

This article organizes what it means to use SVGO and why manual checking as XML is needed afterward.

What is SVGO?

SVGO is a tool for optimizing SVG files.

It is used to remove unnecessary attributes and metadata and make SVG lighter. In the official repository, you can check usage, plugins, and configuration options.

URL: https://github.com/svg/svgo

The use covered here assumes that you check official information and run it in a local environment. If you upload SVG to an online optimization service, information inside the XML and the filename may be sent to an external service.

SVGO is useful, but it is not a dedicated anonymization tool.

Its main purpose is optimization. It does not judge and remove all information related to anonymity.

What tools can reduce

Depending on SVGO settings, comments, metadata, unnecessary attributes, empty elements, and similar content may be reduced.

Optimization is an important pre-publication step.

However, optimization and anonymization are not the same.

Why manual checking is necessary

Tools do not fully judge the meaning of strings.

For example, whether the ID project-alpha is an internal project name or just a shape ID cannot be understood without context. Whether a layer name such as school-map relates to anonymity also changes depending on the post content.

For anonymity, look not only at the file structure, but also at meaning.

This check of meaning is ultimately done by a human.

Manual checking flow

After optimizing with SVGO or a similar tool, open the SVG in a text editor.

Check in the following order.

Searching only for your own name is not enough.

Also check company names, school names, department names, project names, email addresses, place names, old handles, and internal abbreviations.

Visual checking is also necessary

Even if the XML is clean, information visible as an image may remain.

Logos, signs, maps, school emblems, name tags, user names, screen notifications, and distinctive chart designs are not removed by optimization.

SVG must be checked both for its XML contents and for its appearance as an image.

One side alone is not enough.

Choosing between SVG and PNG

When anonymity is needed, publishing after converting to PNG or a similar format instead of SVG is also an option.

If you convert to PNG, information such as XML comments and IDs will generally no longer appear on the surface.

However, information visible as an image remains even after PNG conversion. In addition, metadata may be attached to the converted image.

Which format is better changes depending on purpose and risk.

If you do not need to publish it as an editable diagram, PNG conversion is also an option.

Manage configuration files and source files too

When using SVGO, think about not only the processed SVG but also how you handle configuration files and source files.

If you share source files in the same folder, pre-optimization information may be handed over together. Configuration files may contain project names or internal comments.

For anonymity, it is not always enough to look only at the processed file.

Check whether source files or notes are mixed into the folder or zip you upload.

Even with automation, look at it yourself at the end

If you use SVGO with the same procedure every time, automation is useful.

However, automation does not remove the need for checking. Rather, it is preprocessing so a human can check at the end.

After automatic processing, open the contents in a text editor, display it in a browser, and check the filename and bundled files.

For high-risk files, also consider having another person review them. However, that also means handing the file to that person, so choose the consultation contact carefully.

If the publication target is not a single file but a zip or folder, check bundled items as well as the output SVG.

If old SVGs, source data, work notes, or configuration files are mixed in, information leaks from somewhere other than the optimized file.

Summary

SVGO is a useful tool for optimizing SVG.

It may reduce comments, metadata, unnecessary attributes, and similar information.

However, SVGO is not a dedicated anonymization tool. Internal terms, id, class, text elements, filenames, and information visible as an image need to be checked by a human according to context.

Before publication, after processing with SVGO or a similar tool, open the contents as XML and check them.

For anonymity, what matters is not that you processed the file with a tool, but what ultimately remains.

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