Check your own Spanish
Write or paste a Spanish text. This page holds it up against exactly the rules the site itself teaches: 38 constructions Spanish does not have, 24 Latin American words, 144 irregular verbs conjugated as if they were regular, and 42 false friends. Each finding comes with the page on which the rule is explained. Everything runs in your browser; the text never leaves your device.
A closer look pays off.
What it is measured against
Every rule in this checker is on one of these pages — and the same table checks this site’s own Spanish when it is built. A finding without a source would be an assertion; here are the sources, even without you checking anything.
What this checker can do — and what it cannot
It does not check your Spanish. It checks 248 particular things in it. A text with no findings is not a text without mistakes: tenses, word order, articles and everything there is no rule for here are invisible to this tool. The reverse holds, though: whatever it reports is explained on a page of this site.
Three levels of certainty, and the difference matters. A mistake is a construction this site explicitly rules out — there is nothing to weigh up. A spelling is not a mistake but a choice that has to be kept: across most of Latin America a computer is la computadora, in Spain it is el ordenador, and both are right. This site writes the Spanish of Spain; what looks careless is mixing the two in one text. A note is a question rather than a verdict: sensible is a perfectly good Spanish word — it simply means «sensitive», not «sensible», and whoever wrote it may have meant exactly that.
por against para, ser against estar and the subjunctive are left out on purpose. They are where an English speaker goes wrong most often, and none of them can be recognised from a pattern: English has one verb for «to be» and one word for «for», so the Spanish choice is made on meaning, and only the writer knows what was meant. A checker that guesses is wrong often enough that nobody believes it the next time it is right. Each has its own page; here the checker says nothing.
The word list below is information, not a mark. It shows which levels the words of your text sit at in this vocabulary. A text made entirely of words from the first level can be very good, and one full of words from the top levels very bad.