Split CSV by file size: break a list into files that each fit an upload limit
In short: Type the largest file size you can upload, and get a set of CSV files that each fit, with the header in every one and every row whole. Limit: A single row larger than the limit still ends up in a file over the limit.
Upload a CSV or .xlsx file, or paste it with a header row. Type the largest file size you can upload, in MB, KB or bytes, and optionally a row limit. The tool fills one file after another, never cutting a row, repeats the header in each, shows the exact size of every file and lets you download them one by one or all together.
Price: this tool is free. Checking a whole email list is from $9/mo, and the first 100 checks are free with Google, no card. Check your list free nowSee pricing
Sample result
Six example rows under a 110 byte limit make 2 files of 3 rows, 102 bytes each, with the header in both.
- Files
- 2
- Largest file
- 102 bytes
- Rows too big alone
- 0
What this means for you
Smaller files do not show which addresses exist; a check of the whole list does.
- MB, KB or bytes
- Header in every file
- No row cut in two
- Exact size shown
- Size
- CSV
- Import
By SimpleVerifier Team · Last updated · Runs in your browser; nothing you paste is sent to us
Split? Check the addresses before you upload the parts.
- Download the files, or use the check button under the result, which carries the whole list's addresses across.
- Upload or paste it at /verify. Every address gets a live mailbox check, and the first 100 email checks are free with a Google sign-in, no card.
How do I split a CSV into files under a size limit?
- Upload the file as a CSV or .xlsx, or paste the cells with the header row first.
- Type the largest file size the import accepts and choose the unit.
- Optionally add a limit on rows per file.
- Download each file, or all of them at once.
Example
- You enter
- A header and six rows such as Person 1,person1@example.com, with the largest file set to 110 bytes.
- You get
- 2 files of 3 rows each, 102 bytes apiece, with the header in both. A fourth row would make a file 132 bytes, so it starts the next one.
- Limits
- Runs in your browser; nothing is uploaded. It counts a plain UTF-8 CSV; a single row over the limit still sits alone in a file over it.
How is the size counted?
The size of a file is the number of bytes of the CSV the tool writes: UTF-8 text with the header row, a comma between cells and a carriage return and line feed after every row. The size shown for each file is that exact number. One MB here is 1,048,576 bytes and one KB is 1,024.
Other tools may count a megabyte as 1,000,000 bytes or measure the file before it is compressed, so set a limit a little under the real one.
What is never cut?
A row is never split between two files, and quoted cells with commas or line breaks stay whole. The header row is repeated at the top of every file so each can be imported on its own.
A row that is bigger than the limit by itself goes alone in its own file, which is then over the limit. The tool counts such rows so you can shorten the cells in them.
Row counts or sizes?
If an import limits rows and not size, use the email list splitter or set the row limit here and give a very large size. To take one slice of a file by row number, use the CSV row range extractor. To split by what a column holds, use split CSV by column value.
Who uses this tool, and for what?
- Marketers
- Get a large export under an email platform's import size limit.
- Agencies
- Send a client a list in parts small enough to attach to an email.
- Cold emailers
- Load a big lead file into a sending tool that caps each upload.
What can’t this tool tell you?
- A single row larger than the limit still ends up in a file over the limit.
- It counts a plain UTF-8 CSV; other file types and encodings differ in size.
- It cannot know a site's real limit; leave room under the one you were given.
- Only the first sheet of a workbook is read.
Common questions
- Will every file be under the limit?
- Yes, except a single row that is larger than the limit on its own. Each file's exact size is shown, and such rows are counted.
- Is the header repeated in every file?
- Yes. Every file starts with the header row, so each can be imported alone.
- Why do my file sizes differ from my spreadsheet program?
- The size is that of a plain CSV in UTF-8 with CR LF line ends. A workbook file or a CSV saved with a byte order mark is a little different.
- Can I also limit the rows per file?
- Yes. Type a number in the row limit box. A file closes when it reaches either limit.
- Can I download all the files at once?
- Yes. The button saves them one after another, and your browser may ask before saving several files.
- Is my file uploaded?
- No. The file is read and split in your browser and goes nowhere.
A tidy list can still be full of dead addresses.
Extracting, deduplicating and syntax checks all work on the text of an address. None of them can tell whether the mailbox exists. Only the server that hosts it can answer that, through an SMTP check, and that is what the paid product does.
- Upload the cleaned file as it is: CSVs up to 100,000 rows
- A real SMTP mailbox check on every row, with catch-all detection
- Small list? Starter at $9/mo covers 2,500 emails a month, cancel anytime
Plans from $9 a month, cancel anytime, no contract. Sign in with Google and your first 100 email checks are free, no card. The free tools stay free either way.