Question 1

What is a text diff and how does it work?

Accepted Answer

A diff (difference) algorithm compares two texts and identifies which lines or characters were added, removed, or unchanged. The most widely used algorithm is the Myers diff algorithm, which finds the shortest edit script — the minimum number of insertions and deletions to transform one text into another. Added lines are shown in green, removed lines in red, and unchanged lines provide context. The output format originated with the Unix diff command in 1974.

Question 2

What is the difference between character-level and line-level diff?

Accepted Answer

Line-level diff compares whole lines and marks entire lines as added or removed — useful for code, config files, and documents where the line is the unit of change. Character-level (or word-level) diff goes further and highlights the specific characters or words within a changed line that differ — useful for spotting single-character typos, number changes, or minor edits in prose. Most code review tools (GitHub, GitLab) show line-level diff with inline character highlighting.

Question 3

What are common use cases for text comparison?

Accepted Answer

Common uses: comparing two versions of a config file before deploying, checking what changed between two API responses, spotting differences in contract or legal document revisions, comparing code snippets, verifying that a find-and-replace changed only the intended text, reviewing output differences between software versions, and comparing translations of the same document. Git uses diff internally to track all file changes.

Question 4

How do I interpret diff output (+, -, and context lines)?

Accepted Answer

In unified diff format (git diff output): lines starting with + were added in the new version, lines starting with - were removed from the old version, and lines with no prefix are unchanged context lines (shown for reference). @@ -1,5 +1,6 @@ means the following block starts at line 1 in the old file (5 lines shown) and line 1 in the new file (6 lines shown). A line that was modified appears as a - line followed by a + line.

các công cụ miễn phí dành cho lập trình viên web

Trình so sánh văn bản

Cấu hình

Văn bản cũ

Văn bản mới

Khác biệt

Cách Công Cụ So Sánh Văn Bản Hoạt Động

Công cụ làm gì

Các trường hợp sử dụng phổ biến cho lập trình viên

Định dạng dữ liệu, kiểu hoặc biến thể

Các lỗi thường gặp và trường hợp biên

Khi nào nên dùng công cụ này thay vì viết mã