PhET Interactive Simulations (https://phet.colorado.edu/), a project of the University of Colorado Boulder, was founded in 2002 by Dr. Carl Wieman one year after winning the Nobel Prize in physics. Recognizing the difficulties the general public has in understanding science, he shifted his attention to physics education research. He saw the potential of simulations (sims) for bridging the gap between abstraction and understanding–sims can dynamically illustrate invisible phenomena like atomic and chemical interactions, and force and energy relationships. Leveraging the interactive nature of sims, Carl pursued the development of free, high-quality, evidence-based digital resources that could be accessible to anyone anywhere in the world, supporting their curiosity and creativity. Now, more than two decades later, PhET’s mission reflects Carl’s original goals: to advance science and math fluency by pioneering innovation in inclusive interactive sims and fostering community research, design, and practices that inspire agency in teaching and learning.
PhET sims are available for early learners through university education, and are game-like digital environments that allow students to flexibly experiment with a scenario to understand fundamental math and science principles. Sims are akin to virtual laboratories (in science) or digital manipulatives (for math), and are most effective for exploration and laboratory experiences. For example, science students might use a circuit construction kit to explore how current flows through different branches, and they might use a digital voltmeter and ammeter to determine Ohm’s Law. In mathematics, students might use pieces of a digital cake to represent fraction expressions. Unlike a video, students can control the system: re-arranging objects, adjusting sliders, and capturing data. Sim features are designed around a core concept of implicit scaffolding, a framework that provides the information and interactions necessary to encourage student-driven inquiry of STEM concepts, rather than explicitly providing directions.
Educators may use sims in multiple ways across the learning cycle, using a projector for whole-class exploration or on devices with small groups or individual learners. PhET is used across a spectrum of educational environments, including (1) interactive demos, in which students predict, observe, and explain the outcome of a scenario, (2) lab activities in which students perform controlled experiments, or (3) general exploration to build familiarity with a concept.
Since 2002, our usage growth has been exponential, starting as a project for university students to now a global standard for STEM education. PhET provides 250M+ online learning sessions each year (1.9B+ since inception), impacting an estimated 50M learners (excluding offline use). Following school closures due to COVID, PhET saw a 137% increase in use, particularly in developing countries where STEM teaching resources are limited. PhET observes a ~10% increase in use annually.
Beyond organic adoption, PhET’s commitment to being an inclusive, open education resource has led to its integration into hundreds of edtech products, including UNESCO's Learning Passport, Learning Equality's Kolibri, and World Possible's RACHEL servers, bringing PhET to offline and refugee contexts. Open education partners (OpenStax, OpenSciEd, LabXchange) integrate simulations into freely-available curricula. Commercial partners—including McGraw Hill, Pearson, and Classera—contextualize PhET into textbooks and learning management systems reaching millions.
Since 2020, a core element of our wider adoption has been our PhET Global initiative. Through a coordinated effort to invest in teacher leadership and capacity-building that promotes PhET adoption in the context of contextualized, evidence-based instructional practices, PhET has helped to shift the instructional practices of 143,000+ teachers through in-person activities in 38 countries and virtually around the world.
PhET began as a university physics-focused project. It has evolved to include more science content areas (chemistry, astronomy, biology), mathematics (including statistics and data science), and now supports learning experiences starting with kindergarten. Over 20+ years, PhET has needed to adapt to shifts in technology (from Flash and Java to HTML5, and from computers to tablets and smartphones).
A major shift in our work took place in 2016 with our Inclusive Design initiative launch. As a pioneer in interactive digital learning tools, PhET took on the challenge of designing for maximum accessibility. These innovative features include sonification and voicing (for all students) and interactive description (for use with screen readers), allowing students–including those with visual impairments and blindness–to engage fully in the inquiry process.
Recognizing the need for additional sim customization, PhET created PhET-iO, a tool that allows edtech providers and researchers to “wrap” PhET sims into products to incorporate additional scaffolding and adaptive feedback and/or to capture student engagement for research purposes. Hearing the demand from classroom teachers for similar sim personalization needs, in early 2025, PhET launched a new premium product, PhET Studio, that uses PhET-iO as its internal engine to allow teachers to modify sim settings. As an add-on to PhET’s free content, PhET Studio has also provided a new potential pathway for long-term sustainability.
Anyone can access PhET sims for free from our website at phet.colorado.edu–no registration is required. Click on the “Explore Our Sims” button to get started. You can sort sims by subject, grade level, available inclusive features, and local (language). On any sim page, you can either click the “Play” button to immediately begin interacting, or, if you have limited internet, you can download individual sims or the full PhET Desktop App for free, or download the PhET Mobile App ($0.99). If you are a teacher, you can create a free teacher account to get access to 3,000+ teacher-contributed lesson plans and guidelines for using each sim. You can also learn about PhET’s professional development by visiting the “Teaching” menu item and selecting “Virtual Workshops.” For additional professional development options, including bespoke professional learning and graduate coursework for teachers, contact phet-global@colorado.edu.
