About

Sentence boundary detection is harder than it appears. A period after Dr or U.S.A is not a sentence end. This tool parses text using punctuation-aware splitting, assigning each sentence S_i a color from a cyclic palette of 12 distinct hues. The color index follows c = i mod n, where n is the palette size. Misidentifying sentence boundaries corrupts the visual map. The tool handles common abbreviations and ellipses to reduce false splits.

Applications include proofreading long-form writing, analyzing sentence length variation, teaching grammar structure, and preparing annotated texts. The output can be copied as rich text or exported as a standalone HTML file. Note: the parser approximates English sentence boundaries. Heavily abbreviated or non-standard text (code, legal citations) may produce unexpected splits.

Formulas

Each sentence S_i in the input text is assigned a color from a palette of size n using modular arithmetic:

color(S_i) = palette[i mod n]

Where i is the zero-based sentence index and n = 12 for the default palette. This ensures colors cycle after every n sentences. The sentence boundary regex uses the pattern:

split = match(/([^.!?…]+[.!?…]+[\s]*)/g)

A post-processing step merges fragments that follow known abbreviations (e.g., Mr., Dr., e.g.) back into the preceding sentence. The word count per sentence is computed as:

W_i = |trim(S_i).split(/\s+/)|

Where W_i = word count of sentence i, S_i = the i-th sentence string, palette = array of CSS color hex values, n = palette length (12).

Reference Data

Palette	Color 1	Color 2	Color 3	Color 4	Color 5	Color 6	Best For
Rainbow	#E74C3C	#E67E22	#F1C40F	#27AE60	#3498DB	#9B59B6	Maximum contrast between adjacent sentences
Pastel	#E8A0BF	#95C8D8	#B5D6A7	#F0C27B	#C3AED6	#F7B7A3	Soft documents, presentations
Warm	#C0392B	#D35400	#E74C3C	#E67E22	#F39C12	#F1C40F	Emphasis on energy, urgency
Cool	#1ABC9C	#2ECC71	#3498DB	#2980B9	#8E44AD	#16A085	Calm, professional documents
High Contrast	#FF0000	#0000FF	#008000	#FF6600	#800080	#006666	Accessibility, visual impairment
Earth	#8B4513	#556B2F	#B8860B	#6B8E23	#A0522D	#2E8B57	Natural, organic feel
Sentence Length Benchmarks
Very Short		1 - 8 words		Punchy, impactful. Common in fiction dialogue.
Short		9 - 15 words		Ideal for web content. Flesch-Kincaid friendly.
Medium		16 - 25 words		Standard academic and journalistic prose.
Long		26 - 40 words		Complex arguments. Risk of reader fatigue.
Very Long		> 40 words		Legal, technical. Consider splitting.
Common Abbreviations (Not Sentence Ends)
Mr.	Mrs.	Dr.	Prof.	Sr.	Jr.	Honorifics
vs.	etc.	e.g.	i.e.	approx.	dept.	Latin & General
Jan.	Feb.	Mar.	Apr.	Aug.	Oct.	Month abbreviations

Frequently Asked Questions

The parser maintains a list of approximately 30 common English abbreviations. After initial splitting on sentence-ending punctuation, the algorithm checks if a fragment ends with a known abbreviation. If so, the fragment is merged with the next segment rather than treated as a standalone sentence. This reduces false positives but cannot cover every possible abbreviation. Uncommon or domain-specific abbreviations (e.g., "Corp.", "Ltd.") may still cause incorrect splits.

The color assignment is cyclic. With a palette of 12 colors, sentence 13 receives the same color as sentence 1, sentence 14 matches sentence 2, and so on. The formula is color index = i mod n, where i is the sentence number (zero-based) and n is the palette size. For texts with more than 12 sentences, adjacent same-colored sentences will be separated by 11 differently-colored ones, which maintains visual distinction.

Yes. The "Copy Rich Text" button copies the colored text as formatted HTML to your clipboard. Pasting into Word, Google Docs, or any rich-text editor preserves the colors. Alternatively, use "Export HTML" to download a standalone HTML file that can be opened in any browser and printed with colors intact.

The parser treats both the Unicode ellipsis character (…) and three consecutive periods (...) as a single sentence-ending mark. Text following either form starts a new sentence. If the ellipsis appears mid-sentence without a following capital letter and space, the heuristic may still split there. For best results, use the Unicode ellipsis character or ensure spacing is consistent.

Color assignment is purely sequential by sentence index. Sentence length has no effect on which color is assigned. However, the statistics panel displays word counts per sentence, allowing you to visually correlate sentence length with color patterns. If you need length-based coloring, the tool does not currently support that mode.

The tool processes text client-side with no server round-trips. Texts up to approximately 50,000 characters (about 8,000 words or 400 sentences) render instantly. Beyond 100,000 characters, the DOM may become sluggish depending on browser and device. The tool uses debounced rendering (300 ms delay after typing stops) to prevent UI freezing during input.