The apparent backwards motion is a fact you can check with a telescope. 'Do not sign contracts' is not in Parashara. Somewhere between those two, an industry grew.
Mercury is retrograde roughly three times a year, for about three weeks each time. That is real, it is astronomy, and you can verify it. What is not real is the idea that it breaks technology, voids contracts, or explains your week. Classical Vedic astrology has a position on retrogression, it is quite specific, and it is nothing like the version you have been sold.
What is actually happening
Nothing is going backwards.
Mercury orbits faster than Earth. Three times a year it overtakes us on the inside, and while it does, it appears to slide backwards against the fixed stars — the same way a slower car appears to roll backwards when you overtake it on a motorway. The Latin is retrogradus; the phenomenon is parallax.
It lasts about 21 days. It happens to every planet — Venus, Mars, Jupiter and Saturn all do it, and Saturn spends about four and a half months of every year retrograde. Nobody sells you a candle for that one, which should tell you something about which parts of this are astrology and which parts are merchandising.
Rahu and Ketu are always retrograde. Always. Every day of your life. If retrograde motion were the catastrophe it is marketed as, nothing would ever have worked.
What Vedic astrology actually says about it
Retrogression is a condition of a planet, in the same family as combustion and dignity. It says something about how that planet's results arrive. Roughly, in the classical reading:
A retrograde planet turns its results inward and delivers them out of order — often repeating, revisiting, or arriving late.
That is the whole claim. Note what it is about: the planet, and the houses that planet rules in your chart. Not the calendar. Not everybody at once.
There is also a genuine dispute inside the tradition about whether retrograde motion strengthens or weakens a planet, with real authorities on both sides. When a technique's own literature disagrees with itself, "certainty" is the one thing nobody has earned.
So why does everyone say the same three things?
Because "Mercury rules communication, and Mercury is retrograde, therefore communication breaks" is a syllogism a person can write in ten seconds and publish four times a year, forever. It requires no chart, no birth time, and no arithmetic — which means it can be published about everybody simultaneously, which is the only kind of astrology content that scales.
It is also unfalsifiable in the most convenient way: your email did bounce at some point in those three weeks, your flight was delayed once, somebody did misunderstand a text. Twenty-one days is a long time to find three inconveniences in.
What this app does with it
We show it, we mark it, and we refuse to make a season out of it.
Open the Sky page and every body carries its actual direction — direct, retrograde now, or direct · retrogrades before it leaves. The progress bar under it flows backwards while the planet is retrograde, because a planet backing out of a sign at 2° looks identical to one arriving at 2° if all you draw is a position.
What you will not get is a notification telling you to avoid signing things. When Mercury turns, you get told which house it turns in, measured from your own Moon — because that is the only version of this claim that is actually about you rather than about the calendar.
The short answers
Is Mercury retrograde real? The apparent backwards motion is real and astronomical. The effects popularly attributed to it are not supported by the classical literature that the tradition is built on.
Should I avoid signing contracts? No classical Vedic text says this. It appears to be a 20th-century Western addition that migrated into Indian astrology content because it performs well.
Does it affect everyone the same way? No. Under any Vedic reading, a transit is read from your Moon and your lagna, which is why the same sky means different things for two people on the same day. Anything that reads the same for all eight billion of us is a horoscope column, not a chart.
How often, and for how long? About three times a year, roughly three weeks each. The app tells you exactly when, for your chart.
This is the classical layer, which belongs to everyone. What this app adds on top of it — the reading of your specific chart — is described here, including the parts it refuses to guess at.