Jed Fox

@jedfox
374 Followers
214 Following
230 Posts
he/him. views are my own etc etc. it’s spelled ‘evertrue.’ Instruments/profiling tools @ Apple
Websitehttps://jedfox.com
Observablehttps://observablehq.com/@j-f1
GitHubhttps://github.com/j-f1
Twitterhttps://tweets.jedfox.com
Jed FoxFeb 16
Harjas MongaFeb 16

The Xcode 26.4 beta is out with some really cool features in Instruments! Instruments now has a new Run Comparison feature that allows you to compare call trees across runs so you can quickly verify your performance optimizations (or catch any regressions).

We also have a new Top Functions mode. This new top level mode on the call tree makes it really easy to identify the most expensive functions in the trace no matter where they are called from.

Best part is that these features can be used together to help you optimize your code!

Full release notes: https://developer.apple.com/documentation/xcode-release-notes/xcode-26_4-release-notes

Xcode 26.4 Beta Release Notes | Apple Developer Documentation

Update your apps to use new features, and test your apps against API changes.

Apple Developer Documentation
Jed FoxOct 31

RE: https://infosec.exchange/@madcoder/115466826731130245

Now I finally understand why thr C++ member initializer syntax is spelled the way it is

Jed FoxOct 16

The Profiling Tools team at Apple is looking for interns! We work on the Instruments app, delivering performance insights to developers inside and outside Apple. I’ve really enjoyed this team because we get to work with a lot different people to develop useful tools, and build a lot of personal knowledge along the way.

If you’re interested, feel free to DM me your resume or reply with any questions! In person in Cupertino, for students who will be attending college in the 2026–27 school year.

Jed FoxJun 10, 2025
Harjas MongaJun 10, 2025
It's that time of year, WWDC labs! I highly recommend folks to sign up for labs. I will be in the Performance, Power, and stability labs through the entire week. Sign up for a session, whether you have a specific performance issue you want to work through together or just have questions about our existing & new tools. https://developer.apple.com/wwdc25/sessions-and-labs/one-on-one-labs
Sessions & Labs - WWDC25 - Apple Developer

Learn about WWDC25 sessions, group labs, and one-on-one labs.

Jed FoxJun 10, 2025
Harjas MongaJun 10, 2025

This year we have a brand new CPU counters instrument that reimagines what profiling CPU counters looks like, rather than manually configuring HW counters you will be given a guided approach with understandable metrics & documentation in guiding micro-optimizations. We hope that this new tool makes understanding & optimizing your code using CPU counters much more approachable for developers of all experience levels.

Watch this Optimize CPU performance with Instruments talk. This talk covers CPU profiling from the ground up, covering CPU profiler, Processor Trace, and CPU Counters. This is a fantastic talk I would recommend to every developer, especially those new to profiling & performance work.
https://developer.apple.com/videos/play/wwdc2025/308

Optimize CPU performance with Instruments - WWDC25 - Videos - Apple Developer

Learn how to optimize your app for Apple silicon with two new hardware-assisted tools in Instruments. We'll start by covering how to...

Apple Developer
Jed FoxJun 10, 2025
My work project this year (with help from folks across Apple who built out the data source, taught me how various bits of SwiftUI work, and made the UI in Instruments much more informative): a new SwiftUI instrument that can finally tell you why your views are updating! It also gives you a peek into the soup of attributes under the hood :) Grab one of the 26.0 betas for your device of choice and give it a try: https://developer.apple.com/videos/play/wwdc2025/306/
Optimize SwiftUI performance with Instruments - WWDC25 - Videos - Apple Developer

Discover the new SwiftUI instrument. We'll cover how SwiftUI updates views, how changes in your app's data affect those updates, and how...

Apple Developer
Show threadJed FoxNov 8, 2024

fine print: this position currently requires that you be in person in an office in Cupertino 3 days a week.

If you have questions about the role, feel free to reply or DM!

Jed FoxNov 8, 2024

My team at Apple is hiring! We work on all parts of Instruments — from interacting with OS-level data sources to building the UI components that present that information in an understandable and actionable manner. I really love this job because there are so many different kinds of problem to solve, and we sit at the confluence of a wide variety of other teams’ work. It’s also a rare opportunity to work on a native Mac app :)

If this sounds interesting to you, apply here: https://jobs.apple.com/en-us/details/200577790/developer-tools-performance-tools-engineer

Developer Tools, Performance Tools Engineer - Careers at Apple

Apply for a Developer Tools, Performance Tools Engineer job at Apple. Read about the role and find out if it’s right for you.

Jed FoxJul 30, 2024
Mastodon EngineeringJul 30, 2024

We’re growing our product team!

Are you an #iOS Developer who wants to lead our official #Mastodon iOS #App?

This is a remote full-time position and requires an overlap with the CET timezone.

Ideally:

1. You are a senior iOS Developer comfortable with a mature codebase
2. Proficient in #Swift and #Apple Frameworks (UIKit, SwiftUI, Combine)
3. Prior experience with social media networks is a big plus!

For more info/to apply:
https://jobs.ashbyhq.com/mastodon/bc91c481-d30a-4e73-9eb8-ac29f4e905e2

#FediHire #GetFediHired #hiring #mastodev

iOS Developer (m/f/d)

We're looking for a full-time remote iOS Developer to work on our official Mastodon iOS app.

Jed FoxJun 12, 2024
JoachimJun 12, 2024

There is two more Performance Labs for #WWDC24 : tomorrow and on Friday.

We usually have enough spots to talk to anyone who signs up and has a question, so don’t hesitate to do so. If you have a performance issue, even if you don’t know where it comes from or how to even start looking into it, we are happy to look at it together with you.