🆚 PDF 对比（文字差异比较）Compare PDF Files
比较两个 PDF 的文字内容差异：按行或按词对齐，删除的内容标红、新增的标绿，标出所在页码，相同部分自动折叠；可忽略大小写和空格差异，结果可下载为文本报告，适合核对合同、论文和文档修订版本，全程在浏览器内完成。Find the text differences between two PDFs — aligned by line or by word, with deletions in red, additions in green and page numbers for each change, unchanged parts collapsed. Optionally ignore case and spacing, and download the result as a text report. Handy for checking contract, paper and document revisions; runs entirely in your browser.
使用说明与常见问题How-to & FAQ
「PDF 对比（文字差异比较）」是什么？What is the Compare PDF Files tool?
比较两个 PDF 的文字内容差异：按行或按词对齐，删除的内容标红、新增的标绿，标出所在页码，相同部分自动折叠；可忽略大小写和空格差异，结果可下载为文本报告，适合核对合同、论文和文档修订版本，全程在浏览器内完成。Find the text differences between two PDFs — aligned by line or by word, with deletions in red, additions in green and page numbers for each change, unchanged parts collapsed. Optionally ignore case and spacing, and download the result as a text report. Handy for checking contract, paper and document revisions; runs entirely in your browser.
如何使用「PDF 对比（文字差异比较）」？How do I use the Compare PDF Files tool?
在「PDF 对比（文字差异比较）」中，按需设置「比较方式」等选项，然后点击「开始比较」按钮即可。支持拖放文件。In the Compare PDF Files: Set "Compare", then click "Compare". Drag-and-drop files is supported.
能比较哪些差异？What differences does it find?
比较的是两个 PDF 里可提取的文字：增加、删除和修改过的行（或词）。修改会显示为“删除旧内容 + 新增新内容”。图片、颜色、字体和排版位置的变化不在比较范围内。It compares the extractable text of the two PDFs: added, removed and changed lines (or words). A change shows as the old text removed plus the new text added. Changes to images, colours, fonts or layout position are not compared.
按行和按词有什么区别？Line mode or word mode?
按行适合看哪几段被改过，相同的行会折叠，只显示改动附近 2 行；按词会把全文连起来，在原文中直接标出被删和新增的单词，适合找出一句话里改了哪个词。中文没有空格分词，按词模式下一整段中文会作为一个词，建议用按行。Line mode shows which passages changed, collapsing identical lines and keeping 2 lines of context; word mode runs the text together and marks removed and added words inline — best for spotting a single changed word. Chinese has no spaces between words, so a whole run of Chinese counts as one word; use line mode for Chinese.
扫描件可以比较吗？Can scanned PDFs be compared?
扫描件里只有图片没有文字，无法直接比较。可以先用本站的 OCR 文字识别工具把扫描件转成文字，再用文本对比工具比较。Scans contain only images, not text, so they can't be compared directly. Run them through the OCR tool first, then compare the text with Text Diff.
页码不同的文件能对齐吗？What if pages shifted?
可以。比较是在整份文档的文字上进行的，不按页一一对应，所以中间插入或删除了一页，后面的内容仍会正确对齐；每处差异会标出它在 A 或 B 中的页码。Yes. The comparison runs over the whole document's text rather than page by page, so inserting or removing a page in the middle doesn't throw off the rest; each difference is labelled with its page in A or B.
文件会上传吗？Are files uploaded?
不会。两个 PDF 都在浏览器里用 pdf.js 提取文字并比较，不会离开你的设备。带打开密码的文件需要先去掉密码。No. Both PDFs are read with pdf.js and compared inside your browser; nothing leaves your device. Files with an open password need the password removed first.
「PDF 对比（文字差异比较）」免费吗？需要注册吗？Is the Compare PDF Files free? Do I need an account?
「PDF 对比（文字差异比较）」完全免费，无需注册或安装，打开网页即可使用，手机和电脑都能用；输入的内容只在你的浏览器本地处理。The Compare PDF Files is completely free with no sign-up or install and works on phones and desktops; what you enter is processed only in your browser.