COSRX The Vitamin C 23 Serum
By Nur → Last verified 9/12/2026
Price checked 9/12/2026
YesStyle and Stylevana, checked 2026-09-12. Amazon US list price $25.00 matched on 2026-10-17; the Amazon buy box is a third-party seller, not used as basis.
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What we found
Based on how this product compares to others in the serums category, cross-referenced against retailer listings and market data.
Strengths
- + High concentration for users wanting fast, visible brightening results
- + Real formula layers a second, more stable vitamin C form (3-O-Ethyl Ascorbic Acid) alongside the pure 23% ascorbic acid
- + Also contains niacinamide, squalane, and adenosine, not just a single-ingredient vitamin C treatment
Worth knowing
- - Pure L-ascorbic acid oxidizes faster than derivative forms, meaning a shorter shelf life once opened
- - Higher irritation risk for beginners
Key ingredients
These are the ingredients COSRX highlights for this product, cross-checked against general dermatological and cosmetic-chemistry sources, not a full INCI list.
Fragrance: confirmed fragrance-free.
| Ingredient | What it is | What it does for skin |
|---|---|---|
| Pure L-ascorbic acid (23%) | The purest, most potent form of vitamin C, at a high 23% concentration. | A strong antioxidant that can visibly brighten and target dark spots; this form oxidizes (degrades) faster once opened than more stable vitamin C derivatives.Note: Pure ascorbic acid at this concentration can cause tingling or irritation for sensitive or first-time users; patch testing is worth considering. |
| 3-O-Ethyl Ascorbic Acid (stable vitamin C) | A more stable, gentler derivative of vitamin C. | Converts to active vitamin C once in the skin; brightens and fights free radicals with less irritation risk than pure ascorbic acid. |
| Panthenol | Pro-vitamin B5, which converts to pantothenic acid once absorbed into skin. | Hydrates as a humectant, supports wound healing, and has anti-inflammatory, soothing effects on irritated skin. |
| Squalane | A stable, skin-identical oil, usually plant-derived (from olives or sugarcane) in modern formulas. | An emollient that softens skin and helps prevent moisture loss without feeling heavy or greasy. |
| Niacinamide | A form of vitamin B3, one of the most studied ingredients in cosmetic dermatology. | Strengthens the skin barrier by boosting ceramide production, helps even out tone by limiting pigment transfer to skin cells, and can reduce the look of enlarged pores. |
| Adenosine | A compound naturally present in skin cells, used in skincare as an anti-aging active. | Recognized by South Korea's MFDS as a functional anti-wrinkle ingredient at 0.04% concentration, based on clinical studies showing measurable fine-line improvement; a real but modest effect, not a retinoid substitute. |
| Glutathione | An antioxidant naturally produced by the body, also used topically in some brightening formulas. | Helps neutralize free radicals and is marketed for brightening, though topical absorption and efficacy are less established than oral or injectable use. |
What the brand says
COSRX's own marketing claims, not our own findings.
- High-potency vitamin C
- Marketed for hyperpigmentation and dark spots
- Oil-based delivery system
Research-Based
Our assessment comes from pricing, ingredients, and published information, not personal use, the same standard we apply across the site. This product hasn't been hands-on tested yet. See our Methodology for what that distinction means.
Price history
Current price is the lowest we've recorded so far.
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Frequently asked
How much does COSRX The Vitamin C 23 Serum cost per mL?
$1.25 per mL (currently $25.00 for 20 mL).
Has COSRX The Vitamin C 23 Serum been hands-on tested?
Not yet. Our assessment for this product comes from pricing, ingredients, and published information, not personal use, the same standard we apply across the site. See our Methodology for what that distinction means.
Has COSRX The Vitamin C 23 Serum won any awards?
Yes -- NO.1 in Beauty+ Super Cosmetic Awards 2026.
What are the key ingredients in COSRX The Vitamin C 23 Serum?
The ingredients COSRX highlights for this product include Pure L-ascorbic acid (23%), 3-O-Ethyl Ascorbic Acid (stable vitamin C), Panthenol, Squalane, Niacinamide, Adenosine, Glutathione.
Sources
Pricing and availability for this product were verified against the following retailer listings.