PDF Visual Comparison
Compare two PDF pages and highlight visible pixel differences
PDF Visual Comparison — what it does
Render one page from each of two PDFs and compare them pixel by pixel, highlighting visible differences with an adjustable threshold and a count of differing pixels. Where a text diff sees only words, this catches what actually changed on the page — a moved logo, a shifted margin, a redrawn chart.
When this tool helps
- Verifying that a re-exported document is visually identical to the version already approved.
- Catching a layout shift introduced by a template or font change.
- Comparing two versions of a design proof before sending it to print.
How to use it
- Load the first PDF and choose a page number.
- Load the second PDF and choose its page number.
- Set the difference threshold.
- Compare and review the highlighted differences and pixel count.
Accuracy, limits, and good practice
- Raise the threshold to ignore trivial anti-aliasing noise; leave it low when you need to catch a one-pixel shift.
- A zero-difference result is genuinely useful — it is evidence that a re-export or migration changed nothing visible.
- Rendering differences between machines can produce small discrepancies, so compare files rendered in the same session.
Frequently asked questions
Can it compare whole documents?
One page pair per pass. Step through the pages you care about, or compare the pages most likely to have changed.
Why do identical-looking pages differ slightly?
Font rasterisation and anti-aliasing vary subtly. Increase the threshold so those differences are not reported.
Is this better than comparing text?
It answers a different question. Text comparison finds wording changes; this finds visual and layout changes.
Related tools on this site
- Text Cleaner — Remove extra spaces, empty lines, and repeated lines
- Merge PDF — Combine multiple PDF files into one
- Interleave Two PDFs — Alternate pages from two PDF files into one document
Everything above runs inside this page. PDF Visual Comparison needs no account, no upload, and no server round trip — close the tab and nothing is left behind.
PDF 視覺差異比較能做什麼
分別算繪兩份 PDF 的其中一頁並逐像素比較，以可調的差異門檻標示看得見的差異，並統計相異像素數。文字比對只看得到字詞，這裡抓的是頁面上真正改變的東西——商標位移、邊界偏移、圖表重畫。
什麼時候用得上
- 確認重新匯出的文件在視覺上與已核准版本完全相同。
- 抓出範本或字型更換造成的版面位移。
- 送印前比較兩版設計打樣。
使用步驟
- 載入第一份 PDF 並選定頁碼。
- 載入第二份 PDF 並選定頁碼。
- 設定差異門檻。
- 執行比較，檢視標示的差異與像素數。
精確度、限制與實務建議
- 調高門檻可忽略抗鋸齒造成的細微雜訊；需要抓一像素位移時則調低。
- 「零差異」是真正有用的結果——它證明重新匯出或搬遷沒有改變任何可見內容。
- 不同機器的算繪結果可能有細微出入，建議在同一次操作中比較兩份檔案。
常見問題
可以比較整份文件嗎？
一次比一對頁面。請逐頁比較你在意的部分，或挑最可能變動的頁面。
看起來一樣的頁面為什麼有差異？
字型點陣化與抗鋸齒會有細微差別。調高門檻即可不回報這類差異。
這比文字比對好嗎？
它回答的是不同問題。文字比對找的是用字變動，這裡找的是視覺與版面變動。
本站相關工具
- 文字清理器 — 移除多餘空格、空行與重複行
- 合併 PDF — 將多個 PDF 合併為單一檔案
- 雙 PDF 交錯合併 — 將兩個 PDF 的頁面輪流合併為一個檔案
以上步驟全部在這個頁面內完成，PDF 視覺差異比較 不需要註冊、不上傳檔案、也不經過伺服器，關閉分頁後不會留下任何資料。