To split a text file by lines without uploading it, pick a TXT, CSV, MD, or LOG file up to 10 MiB, enter how many lines each part should hold (any whole number from 1 to 100,000), and download each numbered chunk as a separate UTF-8 TXT file. The whole operation runs locally in your browser through the Text File Splitter, so the source file never leaves your machine and no account is required. Each output keeps the original lines intact, including indentation, trailing spaces, punctuation, and Unicode characters, and joins them with standard LF line endings regardless of whether the source used LF, CR, or CRLF. Filenames follow a deterministic pattern based on the original base name plus a three-digit sequence, so you always know what part-001, part-002, and beyond refer to. This works whenever you have a plain-text file that is too large or too unwieldy as a single document and you want each chunk as a standalone file you can open, email, or upload separately.
Line-Based Splitting Versus Delimiter-Based Splitting
Two ideas get confused under the heading of "splitting a text file," and picking the wrong one wastes time. In spreadsheet programs like Excel or Google Sheets, the Text to Columns feature divides a single row into multiple fields using a delimiter such as a comma, tab, semicolon, or pipe. The rows stay intact; the columns inside each row are what change. That operation is field-based, not file-based, and it is genuinely useful for cleaning up names, dates, or address lines that arrived mashed together in one cell.
The Text File Splitter works in a different direction. It takes one plain-text file that already has thousands of rows and divides those rows into several smaller files so each one is easier to email, upload, annotate, or process in a tool that has row limits. The rows themselves are never reorganized; only the boundaries between files change. This is line-based chunking rather than field-based splitting, and the difference matters because the two operations need completely different tools. If you need Excel-style field splitting by delimiter, you will want a delimiter-aware utility; if you need to break a long file into smaller files of N lines each, this tool is built for exactly that.
When Line-Based Chunking Is the Right Answer
Line-based chunking is the right approach whenever your file already has the structure you need and the only problem is size. Server log files, subtitle rows, simple CSV exports without quoted newlines, Markdown notes, and plain text corpora all fall into this category. If you can open the file in any text editor and see a meaningful row on each line, breaking it into 500-line or 1,000-line batches usually gives you files you can actually work with.
A few concrete situations where chunking is the better choice: dividing a 50,000-line log file into ten 5,000-line files for individual review; splitting a long list of URLs or email addresses into separate uploads for a tool that limits batch size; breaking a Markdown manuscript into chapters or sections for easier collaboration; turning a corpus of one-line records into smaller files for batch processing in scripts; sharing a file with a collaborator whose editor struggles past a certain line count. In every case, the row is already a self-contained unit and the goal is simply fewer rows per file. Chunking is the wrong tool only when a single logical record can legally span more than one line, which is why CSV files with quoted multi-line fields need special care.
How to Split a Text File by Lines Without Uploading
Open the Text File Splitter in your browser and follow these steps:
- Click the file picker and choose one TXT, CSV, MD, or LOG file. The file must be no larger than 10 MiB.
- In the lines-per-part field, enter a whole number from 1 to 100,000. This is how many lines each output chunk will contain.
- Click the split button. The tool processes the file locally and reports the total line count together with the number of parts that will be produced.
- Verify that the totals match what you expected, then download each numbered chunk using its individual download button.
- Keep the original file until you have opened at least the first and last parts and confirmed the content looks right.
Each download creates a temporary Blob URL at click time, triggers one browser download, and immediately revokes the URL. Because no long-lived object URL is created during render, the chunks are only generated when you actually click. Selecting a different file or changing the line count clears the previous result, so filenames and counts can never be mistaken for the new configuration. If your browser asks permission for repeated downloads when many parts are requested, grant it once and the remaining parts will download normally.
How the Tool Counts Lines and Names Each Part
The splitter uses the standard rules for plain-text line boundaries. It recognizes CRLF (Windows-style), standalone CR (classic Mac), and LF (Unix and modern macOS) as line terminators, and treats each one as a single boundary. If your file mixes endings, the count stays consistent because every recognized boundary produces exactly one logical line. Output chunks are always joined with LF, so a mixed-ending source becomes uniform inside the downloaded files.
A subtle but important detail: a trailing line boundary starts a final logical line. If your file contains the single character "a" followed by LF, the splitter counts two lines: "a" and an empty line. With a chunk size of one, this produces one part with "a" and a second part that is empty. The rule prevents the tool from silently discarding a source boundary, but it does mean an evenly divisible file can yield an extra empty part at the end. If you want to predict the part count exactly, check whether the file ends with a newline before you submit it.
Filenames follow a deterministic pattern. The original base name is kept, and each chunk receives a three-digit zero-padded sequence with a literal "part" segment. For a file called notes.txt, the output is notes-part-001.txt, notes-part-002.txt, and so on. The extension is always TXT regardless of the input extension, because every chunk is written as a UTF-8 text Blob. The same decoded input and line count always produce the same strings, the same line total, the same part count, and the same zero-padded names, so the output is reproducible and easy to verify.
| Source line ending | Counted as | Output chunk uses |
|---|---|---|
| LF (\n) | One line | LF |
| CR (\r) on its own | One line | LF |
| CRLF (\r\n) | One line | LF |
| Trailing boundary at end of file | Starts a final empty logical line | LF |
Limits, Formats, and What the Splitter Will Not Do
The 10 MiB cap bounds local decoding and rendering and is checked before any chunking happens. Empty files are rejected because there is no meaningful content to partition. If you submit a file larger than 10 MiB, the tool rejects it without producing a partial result. Lines per part must be a whole number from 1 to 100,000; decimals, zero, negative values, and larger numbers are also rejected up front, and an invalid input never yields a partial result.
The splitter does not validate the syntax of the file you give it. It accepts TXT, CSV, MD, and LOG extensions because those are the common plain-text formats, but it does not parse CSV quoting rules, Markdown structure, or log format conventions. A quoted CSV field that legally contains a newline will be split right in the middle of that field, producing invalid CSV fragments in the surrounding parts. JSON, XML, source code, and Markdown constructs that span lines face the same issue. For any of these formats, use a format-aware parser that knows how to keep records together instead of a line-oriented splitter.
Decoding always happens as UTF-8 because the browser reads the file using File.text. A file that is not actually UTF-8, for example a Windows code-page log with a misleading .log extension, can produce replacement characters after decoding. Open one or two representative output files in the application you plan to use them with before treating the chunks as final. There is no server storage, no account, and no retained processing history; the browser reads, splits, and downloads locally. Because no new dependency is introduced, the tool does not create a ZIP archive; each chunk is downloaded individually.
Reproducible Output and a Worked Example
To check your expectations against the tool, try a file with a known line count. Suppose you have a file with 1,000 lines of content that ends with a trailing newline, giving 1,001 logical lines under the documented counting rule. With a chunk size of 500, dividing 1,001 by 500 gives 2 full groups of 500 lines, accounting for 1,000 lines, and a remainder of 1 line. The tool will produce 3 chunks: two parts with 500 lines each and a third part containing the single trailing empty logical line. Without the trailing newline, the same file would produce exactly 2 chunks of 500 lines each.
Running the same file with the same chunk size always produces the same strings, totals, and filenames, so the output is reproducible across runs and across machines. The tool does not rebalance chunks, does not split by byte size, does not split by words, does not detect paragraphs, and does not keep CSV records with embedded quoted newlines together; it is a plain line-oriented operation. Every complete group contains the requested number of lines except the last, which contains the remainder. If your real goal is to divide a file into two equal halves by lines, the guide on splitting a text file in half by lines walks through the same approach with that specific target.