Transliteration, not translation
Runes are an alphabet, not a language. Carvers used them to write Proto-Norse, Old Norse, Old English and other Germanic languages, spelling words the way they sounded. This tool keeps your English words and swaps each letter for a rune, so Thor the thunder god comes out as ᚦᛟᚱ᛫ᚦᛖ᛫ᚦᚢᚾᛞᛖᚱ᛫ᚷᛟᛞ in Elder Futhark. Someone who knows the runes would read English from it, not Old Norse.
The conversion ignores case, because runes have none, and works strictly left to right. At each position it first tries the two-letter combinations the chosen row has a rune for, then single letters. It does not look at pronunciation: the th in lighthouse gets the thorn rune even though no th sound is spoken there, and doubled letters are written twice.
What each alphabet does with awkward letters
Elder Futhark has no separate runes for several Latin letters, so they share. C, k and q all become ᚲ, v and w both become ᚹ, and j and y both become ᛃ. X is written as two runes, k followed by s. All 24 runes of the row can be reached, including ᛜ for ng and ᛇ for ei.
Younger Futhark has only 16 runes, so the sharing is heavier: e, i and j use one rune, as do c, g, k and q, then d and t, then b and p, and finally u, v, w and y. Viking Age carvers worked with the same limits, which is why their inscriptions are harder to read back. The row has no ng rune, so that pair is written with the n rune and the k rune.
The Futhorc is the most generous. It has its own runes for a, o, y, k, q and x, plus ea and oe, so most English spellings survive a round trip. Two letters still share: v is written with the f rune and z with the s rune.
Converting runes back to Latin letters
The switch above the boxes reverses direction and carries the current output across as the new input. Each rune is replaced by one Latin letter or digraph, and the two runic punctuation marks ᛫ and ᛬ become spaces. The result is always lower case. Characters that are not in the selected row are left as they are, so check that the alphabet button matches the runes you pasted.
Where several letters share a rune, the reverse step has to pick one, and it picks the first in alphabetical order. In Elder Futhark king becomes ᚲᛁᛜ and reads back as cing, and wolf reads back as volf. In Younger Futhark king returns as cenc. The Futhorc returns both words intact. Treat reverse output as a reading aid for runes you found, not as a decoded message.
Choosing an alphabet for a name or an inscription
Choose by period. Elder Futhark fits the oldest inscriptions, from before the Viking Age. Younger Futhark is the script of Viking Age Scandinavia and of most surviving runestones. The Futhorc belongs to Anglo-Saxon England and Frisia. For a modern name written for decoration, Elder Futhark and the Futhorc keep more of the spelling, because fewer letters share a rune.
For anything permanent, such as a tattoo, a ring or a memorial, remember what the tool does not know. It does not translate into Old Norse or Old English, it does not apply historical spelling conventions, and it cannot tell you which rune forms a particular region or century used. Have the result reviewed by someone who reads runes before it is cut into skin or stone.
Copying runes into other apps
The output is ordinary Unicode text from the Runic block, U+16A0 to U+16FF, so it pastes into documents, chat apps and design software like any other characters. Whether it displays depends on the font. If you see empty boxes, the device has no font that covers the block, and the person you send it to may be in the same position. For print or engraving, set the text in a font you have checked.
Runes are a script, not a cipher: anyone with a rune chart can read this output. If the aim is to obscure or encode a message, the ROT13 Encoder / Decoder and the Morse Code Translator are the tools for that.