The I Ching is the oldest divination system still in active use - three thousand years old and still asking useful questions. I return to it whenever I want to think more carefully about something. Not because it tells me what to do, but because it rarely lets me off with a shallow answer. The tool below is the one I built to consult it properly.
The I Ching - the Book of Changes - is a Chinese divination text compiled over several centuries, reaching something close to its current form around 1000 BCE. At its core are 64 hexagrams: six-line figures each made of broken and unbroken lines, representing yin and yang in every possible combination. Each hexagram has a name, an image, a judgement and a set of commentaries that accumulated across centuries of use. The system was consulted by emperors, generals and philosophers. Jung wrote about it seriously. It has not gone anywhere.
The traditional casting methods - three coins or 49 yarrow stalks - introduce an element of chance that produces not just a hexagram but potentially a second one via changing lines. A line that is yin in the process of becoming yang, or vice versa, creates a transformed hexagram that speaks to where the situation is heading. The Engine handles all of this: it simulates all three casting methods, identifies changing lines and generates both the primary and transformed hexagrams where applicable.
How you use it is entirely up to you. Some people treat it as a genuine oracle - a channel for something beyond ordinary reasoning. Others use it as a structured thinking prompt, the way you might flip a coin not to let the coin decide but to notice your reaction to the result. I sit somewhere between those positions. What I can say with confidence is that the hexagrams are genuinely interesting as symbolic objects, and the process of casting and reading produces a kind of focused attention that is useful in itself, regardless of what you make of the mechanism behind it.
The three casting methods the Engine supports are not interchangeable in feel, even if they are statistically equivalent. The coin method is faster and produces a more uniform distribution. The yarrow stalk method - or its simulation - introduces slightly unequal probabilities for moving lines, which traditionalists argue makes it more precise. The random generator is the most direct. I would suggest starting with coins and moving to yarrow stalks once you are familiar with the process. The hexagrams themselves do not change. What changes is how you arrive at them.
The I Ching Engine is free to use, with no account required and no results held behind a paywall. It supports all three traditional casting methods and produces the full text for both primary and transformed hexagrams where changing lines are present.
If you have suggestions - a hexagram reference library, a reading journal, aspect comparisons between hexagrams - the contact page reaches me directly. The I Ching rewards sustained engagement. The Engine is a place to start.
"The hexagram does not predict. It orients."
Marcus Lee - The Arcana Engine