Your CSV is probably fine. Your encoding is the problem.

Mojibake in Shopify imports means your file is saved in ANSI, GBK or Shift-JIS. Re-save as UTF-8 with these steps.

Three common sources of mojibake

The garbage usually enters the file in one of these ways:

Excel 'Save As CSV' keeps the system locale encoding instead of UTF-8.
Export tools from other platforms (Amazon, Etsy, AliExpress) save in their own regional encoding.
A text editor converted the file with the wrong character set and replaced unknown bytes.

ShopTools re-exports your CSV as UTF-8 with BOM, fixes quote and separator damage caused by encoding conversions, and keeps every product intact.

Open the CSV in a code editor or Notepad++ - not Excel.
Confirm the current encoding (ANSI/GBK/Shift-JIS shown in the status bar).
Choose 'Encode in UTF-8' and save the file.
Re-import into Shopify and verify one Chinese or accented product name before the full import.

Before: Title: 链????褰? 套装 (mojibake after GBK file read as UTF-8) After: Title: 连衣裙套装 (correct Chinese)
Before: Excel Save As CSV (ANSI default on regional systems) After: Save As CSV UTF-8 (with BOM) from the editor

Chinese and Japanese stores: GBK and Shift-JIS files are the usual culprits
Any store importing regional CSVs: Supplier files from Asia are frequently ANSI-encoded

Why does my CSV look fine in Excel but break in Shopify?: Excel displays the file using your system encoding, so it looks correct locally. Shopify assumes UTF-8 and reads the raw bytes differently.
What is the BOM for?: A UTF-8 byte-order mark tells Excel to open the file as UTF-8 instead of guessing. Shopify accepts it and it prevents Excel from mangling the file on re-save.
Will re-saving as UTF-8 change my data?: No - it only changes how the bytes are stored. All characters are preserved.
Can ShopTools fix an already-broken file?: If the original encoding can be detected, yes. The repair pass re-exports clean UTF-8 and fixes quote damage from the conversion.