Monday, April 4, 2022


Howard Oakley (Hacker News):

Over the last year or so Mac users have run into problems that appear related to a background service named triald. Some report it stealing huge amounts of CPU, others associate it with various glitches, and a few have noticed gigabytes of disk space apparently being taken up by its folder at ~/Library/Trial, and in their Time Machine backups.


The Trial root directory can readily occupy substantial amounts of disk space: on my production Mac, it appears to contain 1.47 GB in 148,618 items, which is a hefty chunk in backups.


Trial appears primarily concerned with gathering data from Experiments distributed via CloudKit. These notably include ML features such as Visual Look Up.


Trial’s root directory at ~/Library/Trial should be added routinely to all backup exclusion lists. Apple should add it to Time Machine’s system exclusions at the earliest opportunity.

Howard Oakley:

Last week we celebrated the fifth anniversary of APFS, the file system which Apple secretly rolled out to millions of iPhones and iPads on 27 March 2017. It was also the week when we discovered that services introduced over a year ago in macOS Big Sur appear to conduct ‘trials’ and ‘experiments’ on our Macs. While Apple came clean about APFS [how previous software updates did test filesystem migrations] just over two months later, it shows no sign of explaining what’s been happening on our Macs.


The principle here is treating adults as adults, with respect. When you’re going to change something which you suspect could affect them, you communicate, inform, and obtain their consent.


As we don’t know what triald does collect, and what it might share by way of results, it’s impossible for us to know how Apple considers its activities relate to its long and detailed statements on privacy. Although I’m sure those who already accuse Apple of not adhering to its high ideals will be as sceptical as ever, I’m confident that triald does comply with its stated policies in all but one respect: nowhere in those pages do I see any reference to trials or experiments, except in the very different context of health studies.

Update (2022-04-12): Howard Oakley:

As we start to explore Apple’s latest undocumented service, Trial, gaining easy access to its log entries becomes important. I’ve therefore added another readymade log browsing option to my free utility Mints.


Trial appears to be involved in all parts of macOS which benefit from ML, including Siri, natural language processing, Photos library and other image analysis, Spotlight search ranking, and Safari search ranking and other features. This is a non-trivial system.

Howard Oakley:

Currently, the major supplier of apps using Core ML is Apple. Trial, and possibly a sibling going under the name of Biome which also has its own root directory in ~/Library, appears to be Apple’s system for deploying new and updated models for use in Siri, Photos image analysis and recognition, Visual Look Up, Live Text, and other features in Big Sur and Monterey.


It still remains strange that Apple should use terms like trial and experiment, if these are just model updates. Despite what some may think, ML doesn’t normally proceed by running large-scale trials or experiments across user systems.

2 Comments RSS · Twitter

Old Unix Geek

I didn't agree to any sharing of data with Apple, yet I have that directory.

I don't use SIRI, but triald still went ahead and installed "SIRI" trials. They are apparently encrypted. I'm guessing they are experiments to see whether error rates go down with different ML models of english, chinese, etc.

There's a trial database in ~/Library/Trial/... which seems to keep track of what "experiments" were downloaded, and it's full of SQL functions checking what kind of device it is running on. It also contains certificates which I am guessing are used to validate these "experiments".

A quick perusal of the disassembly of triald indicates it contains code to start a server, and to start up sandboxes. One would presume that these sandboxes are used to run experiments.

Frankly, I find this an extraordinary breach of trust by Apple. Whose computer is this device my company supposedly bought?

And wouldn't this constitute a breach of the EU's GPDR? I'm no lawyer, but it doesn't seem Transparent, Specific, or Explicit as defined by the GPDR to me ( ) since I don't recall authorizing it, or even being informed of its existence.

Perhaps someone currently residing in the EU could tell us if ps aux | grep triald shows a running process, and whether they have a ~/Library/Trial directory...

Anyway, I should get back to work...

@ OUG: yes and yes.

But I did agree to data sharing, so I can't comment on that part. If they do gather (and upload!) even without data sharing disabled, whether it relates to GDPR depends in part on whether the data is PII.

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