Log File Splitter

A log file that is too big is a log file that is useless. Editors refuse to open it, upload forms reject it, databases hit row or byte limits, and a mail client bounces the attachment. Before working with a monster log it has to be cut into pieces. Log File Splitter does that split in three different, purpose-built ways: by line count, by target file size, or by the date on each line.

Line-count splitting gives predictable chunks — every 10,000 lines, every 100,000 lines, whatever number is chosen — ideal for feeding a parser that takes bounded batches one at a time. Size splitting targets a byte budget (say 4 MB per chunk for an upload limit) and respects it without ever cutting a line in the middle: whole lines are accumulated into the current chunk until the next one would push it over the target, at which point the chunk closes and a new one starts, so every chunk stays independently parsable. Date splitting turns a mixed multi-day file into per-day pieces, using a configurable regular expression to read the date token out of each line and grouping consecutive lines that share it into the same chunk, so a month-long file becomes one chunk per day in the order the days actually appear.

Every chunk previews in its own panel with its own line count and byte size, plus copy and download buttons, and a Download all action fetches every chunk in one pass with sequential file names. Summary cards above the chunk list report the total line count of the input, how many chunks were produced, the input size in bytes, and the size of the largest single chunk, so it is easy to confirm the split behaved as expected before exporting anything.

• Split by line count — fixed batch sizes, non-overlapping and gap-free, ideal for parsers and shippers that expect bounded batches.
• Split by size — target a byte budget in KB without ever splitting a line in half; a chunk closes exactly when the next whole line would overflow it.
• Split by date — consecutive lines sharing the same extracted date are grouped into one chunk, turning a multi-day file into clean per-day pieces automatically.
• Configurable date pattern — a regular expression drives the date extraction, so formats beyond the default YYYY-MM-DD are just as easy to split by.
• Unknown-date grouping — lines that do not match the date pattern are grouped under an “unknown” label rather than being dropped or scattered.
• Per-chunk actions — copy or download any single chunk directly from its preview panel.
• Download all — fetch every chunk in one click with sequentially numbered file names.
• Summary cards — total lines, chunk count, input byte size, and the size of the largest chunk produced.
• 100% local — nothing leaves the browser, no upload, no server round trip.

1. Paste your log into the text box, or click Load sample to try the three modes against a small multi-day example.
2. Pick a mode. Line count for fixed-size batches, size for upload or storage limits, or date for turning a multi-day file into per-day pieces.
3. Set the parameter that matches the mode: lines per chunk, target size in KB, or the date-matching regular expression.
4. Click Split. The summary cards report the total input lines, how many chunks were created, the input size, and the largest chunk produced.
5. Review each chunk in its own preview panel, then copy or download it individually, or use Download all to grab every piece at once.

Example 1 — Upload limits. A SaaS importer accepts files up to 5 MB. Splitting by size with a 4,000 KB target turns a 63 MB export into a set of safely sized chunks that upload one after another without a single line broken across two files.

Example 2 — Per-day archives. A month of service logs sits in one file. Splitting by date, with the default YYYY-MM-DD pattern, produces one chunk per calendar day for daily archival or per-day review.

Example 3 — Batch parsing. A downstream parser handles 50,000 rows at a time. Splitting by line count at 50,000 produces exactly that many rows per chunk (except the final, shorter one), ready to feed in sequence.

Example 4 — Mixed logging format. A vendor appliance sometimes omits the date prefix on continuation lines. Splitting by date still groups those undated lines correctly under the “unknown” label instead of silently dropping them from the output.

• Bounded, addressable pieces produced from a log of any size, in whichever unit actually matters for the downstream system.
• Never splits a line in size or date mode — every chunk stays independently parsable.
• Full coverage, no gaps or duplicates — every input line lands in exactly one chunk, in the original order.
• Per-day grouping built in for archive and audit workflows, with no manual date-bucketing required.
• Per-chunk export plus download all — grab one piece or the whole set with a single click.
• Private — all splitting happens locally in the browser; the log is never transmitted.