The Vitamin C 13 Serum

COSRX The Vitamin C 13 Serum is the everyday member of the brand's vitamin C line — water-based, thin, and deliberately milder than the 23% version. It carries a faint yellow cast, which COSRX points to as a sign of pure vitamin C sitting in the bottle.

What it actually does

• Brightens with daily use. COSRX frames it as something you reach for every morning, the way you would a vitamin, rather than a weekly treatment.
• Works on dark marks over time. The brand says consistent use fades blemishes, dark spots and freckles while evening out overall tone.
• Hydrates as it treats. Being water-based, it delivers moisture alongside the vitamin C instead of leaving skin tight.
• Sinks in without tack. The texture is watery and light, and it absorbs well with no sticky film left behind.
• Gentler than the 23% serum. COSRX positions this as the lighter, fresher-feeling option of the two — the reason it suits daily rather than occasional use.

How to use

1. Cleanse, then tone. The serum goes on after both steps.
2. Dispense a few drops. You do not need a flood of it.
3. Massage outwards. Use your fingertips and work from the centre of the face towards the edges until it has absorbed.
4. Follow with the rest of your routine. Moisturiser next, and sunscreen if it is morning.

Is it right for you?

Questions

How is this different from the Vitamin C 23 Serum?

COSRX describes the 13 as lighter and more refreshing, which is what makes it the one you can use every day. The 23 is the stronger sibling.

Why does it look slightly yellow?

The brand explains the yellowish tint as an indicator that pure vitamin C is in the formula. It is expected, not a fault.

Can I use it every single day?

Yes — daily use is exactly how COSRX intends it to be used, and the dark-spot and tone claims are tied to using it regularly.

Where does it sit in my routine?

After cleanser and toner, before your heavier steps. A few drops patted in with fingertips is all the application needs.

How long does delivery take?

Delivery takes 3 to 21 working days, depending on availability. Working days exclude weekends and official holidays.

How can I pay?

Credit card, debit card, Instapay and mobile wallets — no cash on delivery.

What if my order arrives damaged?

Report it within 1 day of delivery with a photo. We accept returns for defective, damaged or expired items only, and refunds go back to your original payment method within 15–30 days.