About

Unicode combining characters (range U+0300 - U+036F) are non-spacing marks that attach to the preceding base character without advancing the cursor. Incorrect usage produces mojibake or corrupted displays across mail clients, databases with improper normalization, and legacy systems that strip or misinterpret multi-byte sequences. This tool inserts one or more combining diacritical marks after each base character in your input, generating real Unicode output - not images or SVG hacks. It handles stacking order, avoids double-application on existing combining marks, and respects the 5000-character safety limit to prevent browser rendering stalls from excessive mark accumulation.

Common applications include linguistic annotation (IPA transcription requires precise mark placement), mathematical notation where combining overlines (U+0305) denote repeating decimals, and creative “Zalgo” text effects that stack multiple marks vertically. The tool distinguishes between above, below, overlay, and enclosing mark categories so you can control vertical placement. Pro tip: some fonts render stacked marks poorly - test output in your target application before publishing.

Formulas

The combining character insertion algorithm processes each character in the input string and classifies it by Unicode code point. For a given input string S of length n and a set of selected combining marks M, the output string O is constructed as follows:

for each c_i in S:
append c_i to O
IF isCombining(c_i) = FALSE:
for each m_j in M:
repeat m_j × k times, append to O

Where k is the stacking intensity (1 - 10). The function isCombining(c) returns TRUE when the code point falls within U+0300 - U+036F, U+1AB0 - U+1AFF, U+1DC0 - U+1DFF, U+20D0 - U+20FF, or U+FE20 - U+FE2F. This check prevents combining marks from receiving additional marks, avoiding uncontrolled recursive stacking. Output length is bounded by n × (1 + |M| × k).

Reference Data

Character	Unicode	Name	Position	Example (on 'a')
̀	U+0300	Combining Grave Accent	Above	à
́	U+0301	Combining Acute Accent	Above	á
̂	U+0302	Combining Circumflex Accent	Above	â
̃	U+0303	Combining Tilde	Above	ã
̄	U+0304	Combining Macron	Above	ā
̅	U+0305	Combining Overline	Above	a̅
̆	U+0306	Combining Breve	Above	ă
̇	U+0307	Combining Dot Above	Above	ȧ
̈	U+0308	Combining Diaeresis	Above	ä
̊	U+030A	Combining Ring Above	Above	å
̋	U+030B	Combining Double Acute	Above	a̋
̌	U+030C	Combining Caron	Above	ǎ
̐	U+0310	Combining Candrabindu	Above	a̐
̒	U+0312	Combining Turned Comma Above	Above	a̒
̓	U+0313	Combining Comma Above	Above	a̓
̔	U+0314	Combining Reversed Comma Above	Above	a̔
̖	U+0316	Combining Grave Below	Below	a̖
̗	U+0317	Combining Acute Below	Below	a̗
̣	U+0323	Combining Dot Below	Below	ạ
̤	U+0324	Combining Diaeresis Below	Below	a̤
̥	U+0325	Combining Ring Below	Below	ḁ
̦	U+0326	Combining Comma Below	Below	a̦
̧	U+0327	Combining Cedilla	Below	a̧
̨	U+0328	Combining Ogonek	Below	ą
̭	U+032D	Combining Circumflex Below	Below	a̭
̮	U+032E	Combining Breve Below	Below	a̮
̰	U+0330	Combining Tilde Below	Below	a̰
̱	U+0331	Combining Macron Below	Below	a̱
̲	U+0332	Combining Low Line	Below	a̲
̳	U+0333	Combining Double Low Line	Below	a̳
̴	U+0334	Combining Tilde Overlay	Overlay	a̴
̵	U+0335	Combining Short Stroke Overlay	Overlay	a̵
̶	U+0336	Combining Long Stroke Overlay	Overlay	a̶
̷	U+0337	Combining Short Solidus Overlay	Overlay	a̷
̸	U+0338	Combining Long Solidus Overlay	Overlay	a̸
⃝	U+20DD	Combining Enclosing Circle	Enclosing	a⃝
⃞	U+20DE	Combining Enclosing Square	Enclosing	a⃞
⃟	U+20DF	Combining Enclosing Diamond	Enclosing	a⃟
⃠	U+20E0	Combining Enclosing Circle Backslash	Enclosing	a⃠

Frequently Asked Questions

Combining character rendering depends on the font's OpenType GPOS/GDEF tables and the text shaping engine (HarfBuzz, DirectWrite, CoreText). If a font lacks anchor points for a specific combining mark, the mark will appear misaligned or overlap adjacent glyphs. Monospace fonts and system fallback fonts handle stacking particularly poorly. Test your output in the target application with the intended font before deployment.

A precomposed character like "é" (U+00E9) is a single code point. The equivalent combining sequence is "e" + U+0301 (two code points). Unicode Normalization Form C (NFC) converts combining sequences to precomposed equivalents where they exist. Form D (NFD) does the reverse. This tool always outputs combining sequences (NFD-style), which may be normalized by downstream systems. If your output appears to lose marks, check whether the receiving system applies NFC normalization.

The Unicode standard imposes no hard limit on combining character sequences. However, the Unicode Consortium recommends a Stream-Safe Text Format limit of 30 trailing non-starters. In practice, browsers begin to exhibit rendering artifacts (clipping, overflow into adjacent lines) at around 10-15 stacked marks depending on the font and mark category. This tool caps stacking intensity at 10 repetitions per mark to balance visual effect with rendering stability.

Yes. In JavaScript, Python 3, and most languages, string length counts code units or code points, not grapheme clusters. The string "a" + U+0301 has length 2 in JavaScript despite appearing as one visible character. Use the Intl.Segmenter API or a grapheme cluster library when you need to count user-perceived characters. Database VARCHAR columns may also truncate mid-sequence, corrupting the output.

Absolutely. The string "café" can be encoded two ways: with precomposed "é" (U+00E9) or as "e" + U+0301. These are canonically equivalent but not byte-equal. A naive string comparison (=== in JavaScript) returns false. Always normalize strings with NFC or NFD before comparison. SQL databases vary: PostgreSQL respects Unicode equivalence with the "und-x-icu" collation, while MySQL's utf8mb4_general_ci does not distinguish combining sequences from precomposed forms.

Zalgo text stacks numerous combining marks (above, below, and overlay) on each base character to create a visual "glitch" or "corrupted" appearance. It exploits the fact that browsers attempt to render all combining marks even when they overflow the line height. Typically 5-15 randomly selected marks from each positional category are applied per base character. This tool provides controlled Zalgo generation through the stacking intensity slider and category filters, giving precise control over the effect density.