DNS Record Splitter
Split a long TXT value into the 255-byte quoted strings DNS actually requires.
Need to generate a DKIM key instead of just splitting one? Use the free DKIM generator.
How to Use the DNS Record Splitter
Paste the long value
A DKIM public key is the most common case, but any long TXT value works.
Read the byte count
DNS caps a single TXT string at 255 bytes – anything longer needs splitting.
Copy the split result
Either the zone-file format or the individual chunks, whichever your DNS host's UI expects.
Why 255 Bytes, Specifically?
DNS TXT records are defined as one or more character-strings, and the DNS wire format (RFC 1035) encodes each character-string's length in a single byte – capping any one string at 255 bytes. A long value (most often a DKIM RSA public key, which runs to hundreds of base64 characters at 2048 bits) has to be broken into multiple character-strings within the same TXT record. Resolvers concatenate them back together when the record is read, so the split is invisible to anything actually using the record – it only matters for how you enter it.
Next Steps
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Start free →Frequently Asked Questions
Is this DNS record splitter free?
Yes – it runs entirely in your browser, no signup, and nothing you paste is sent anywhere.
Why does a TXT record need splitting at all?
A single TXT string is capped at 255 bytes by the DNS protocol itself (RFC 1035). A 2048-bit RSA DKIM public key, once base64-encoded, is comfortably over that – so it has to be published as multiple quoted strings that DNS concatenates back together when read.
Does splitting change the value at all?
No – it's purely mechanical. The concatenated result is byte-for-byte identical to what you pasted; splitting only affects how it's represented across multiple quoted strings.
My DNS host's UI only has one text box – what do I paste?
Most providers that only offer a single box handle the 255-byte splitting internally and just want the raw, unsplit value – try pasting it whole first. The split output here is for providers (or zone files) that explicitly expect multiple quoted strings.
Does this work for values other than DKIM keys?
Yes – any TXT value over 255 bytes needs the same treatment, DKIM keys are just the most common real-world case.