Which of the two forms you need
Before you ask how to legalize a Birth Certificate, settle which of the two Italian forms you need. The short certificate gives the name, the place and the date. The full extract, the estratto per copia integrale, repeats all that and adds the parents plus any later notes the register has picked up.
Most foreign desks want the full extract. A marriage office abroad needs the parents named on the face of it. A citizenship file needs the notes about later marriages or a change of name. Order the short form only when the desk has told you in writing that it will be enough.
The Comune that holds the entry
The embassy legalization of a Birth Certificate in Venice starts at the Comune that entered the birth in its register, not at the one where you live now. If the birth happened elsewhere and was later transcribed into the books here, that local extract is still the Italian record and it is the sheet you want.
A paper from the hospital is not a civil record, and no office will seal it. Nor will a family book or a baptism sheet stand in. What travels is the sheet a civil-status clerk signs, printed fresh from the register on the day you ask for it.
The state counter in the province
The consular legalization of a Birth Certificate in Italy then needs a state seal. That comes from the Prefettura, the government office sitting in each Italian province, which legalises administrative papers. Its clerk holds a specimen for each civil-status officer and compares your sheet against it.
Nothing judicial is in play, so the court counter has no part in this file. A decree or a deed drawn before a notary would go to the Procura della Repubblica instead. A register extract signed by a Comune clerk sits squarely on the administrative side, which keeps this route short.
The consular step and the bill
Two amounts land on the bill. The Italian side takes a €16 tax stamp (marca da bollo), fixed to the file before it is lodged. The destination consulate then charges a consular fee of its own, set by that mission alone, so ask them for the current tariff in writing.
Reckon on 10–15 business days once a complete file is in hand. Where the mission opens a faster lane, express work is 3–5 business days. The counter wait at the Comune sits before all of that, so order the extract in the same week you decide to begin.
What the record unlocks abroad
People legalize a Birth Certificate in Venice to marry abroad, to claim citizenship through a parent, or to enrol a child in a foreign school. Survivor pension files call for it too. In each case the office abroad is checking a chain of names, and this extract is the first link in that chain.
Citizenship files are the heaviest users of all. They often need extracts for a parent and a grandparent as well, each sealed in its own right. Work the full list out with the consulate first, because ordering them one at a time doubles the waiting for no gain.
Freshness, translation and acceptance
Order the embassy attestation of a Birth Certificate in Venice only after you know the destination wants that step. Whether consular legalisation is called for depends on the destination country, so ask the receiving authority to say so in writing. A number of destinations take a single-step certification and stop there.
Age matters more than people expect. Many desks will not read an extract issued more than a few months back, because the register may have moved on since. Confirm the required language with the receiving office in writing as well, and we will have the text sworn before a Tribunale in Italy.