Uppskriftin er á síðunni.

The recipe is on the page.

Breakdown of Uppskriftin er á síðunni.

• vera: to be
• á: on
• síðan: the page
• uppskriftin: the recipe

Questions & Answers about Uppskriftin er á síðunni.

Why is uppskrift written as uppskriftin?

Because Icelandic often attaches the definite article to the end of the noun as a suffix.

• uppskrift = a recipe
• uppskriftin = the recipe
  Here the speaker is referring to a specific, known recipe, so the definite form is used.

What gender is uppskrift, and does that affect the ending -in?

uppskrift is feminine. In the nominative singular definite, many feminine nouns take the ending -in (or -in attached to the stem), giving uppskriftin.
The exact definite endings vary by gender and declension class, but gender is the reason you don’t see a masculine-style ending like -inn here.

Why is it Uppskriftin er... (nominative) and not some other case?

Because uppskriftin is the grammatical subject of the sentence, and Icelandic subjects are typically in the nominative case.
The verb er (is) links the subject to a location phrase (á síðunni).

What does er tell me grammatically?

er is the present tense, 3rd person singular form of the verb að vera (to be).
It agrees with a singular subject like uppskriftin. There’s no separate word for am/are/is—it’s all forms of að vera.